Talk:IEEE Std 260.1-2004

Customary Inch-Pound Units

I'm struggling a bit trying to understand what is meant by "Customary Inch-Pound Units". I don't have a copy of IEEE 260.1 but NIST SP-1038 says this:

3.2 Inch-Pound Units: Units based upon the inch, pound, and gallon were historically derived from the English system and subsequently were re-defined as multiples of SI Units in U.S. law beginning in 1893.

This makes no sense to me, because we have two units of length here (inches and gallons), one of mass, and none of time. So it's not a system of units in the traditional sense like MKS or CGS.

I changed the link to point to Foot–pound–second system. If they really are talking about a system of units, this seems like the right place to go. Kendall-K1 (talk) 23:32, 7 October 2017 (UTC)

It seems likely that by the title IEEE are simply trying to give a sense of the collection of units that they list, not a formal system of units; the phrase "inch-pound units" might in general mean "units in common use in the English-speaking world (or maybe only the US) before metrication". As such, there would be no attempt at consistency or completeness. It seems likely that they would not add any time units outside of their treatment of SI units, essentially only expanding SI's treatment of units accepted for use with SI. Listing such units would have value because a uniform set of symbols and even definitions for modern use is helpful, considering that they still get used (causing our grandchildren much unneeded pain because we refuse to be sensible). I do not have access to the standard either, otherwise I would have added a lot of detail already. Once we have a sense of which customary units they cover, the best target might become evident, but until then your guess is as good as any. —Quondum 02:56, 8 October 2017 (UTC)

Now I'm tempted to change it back. Your reasoning as to why they left out seconds makes sense. Although why say "inch-pound"? I'm not sure IEEE really knew what they were doing with this one. They don't even know what the title of this spec (that they wrote) is. Kendall-K1 (talk) 03:09, 8 October 2017 (UTC)

I do have a copy. The impression that I get when reading it is close to Quondum's interpretation. The standard represents a valiant (and IMO serious) attempt to provide standardized symbols for units that are widely used, including the SI. For the SI units their work duplicates material from existing BIPM and ISO documents, but the "customary" units are by and large deprecated by BIPM and ISO, so I guess they're trying to fill that vacuum. Dondervogel 2 (talk) 08:14, 8 October 2017 (UTC)

Perhaps Dondervogel 2 can at least clarify the title issue. What is the exact title that is displayed in IEEE Std 260.1-2004 document itself? Also, I can see the title having originated before they did know exactly what they were doing (i.e. put it down to "history"), since it was almost identical on

• IEEE 260-1978: IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units),
• IEEE 260.1-1993: American National Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units) and
• IEEE STANDARD 260.1-2004: IEEE Standard Letter Symbols for Units of Measurement (SI [...] Customary Inch-Pound Units, and Certain Other Units).

Dondervogel's characterization of the intent sounds highly plausible. The question is really what belongs in the "[...]". —Quondum 12:40, 8 October 2017 (UTC)

The full document title (copy-pasted from the title page) is "IEEE Standard Letter Symbols for Units of Measurement (SI Units, Customary Inch-Pound Units, and Certain Other Units)". Dondervogel 2 (talk) 13:37, 8 October 2017 (UTC)

Okay, great. This exactly matches the title from the document I used, and what is presently in the article. As we expand the list (at least with the most useful/controversial symbols not covered by SI documents), I wonder whether this would be deemed copyright violation? —Quondum 20:33, 8 October 2017 (UTC)

If we were copying verbatim, and doing so extensively, that might be considered a breach of copyright. I'm no expert, but for as long as we are selective, and do not copy verbatim, I would not expect a problem. We could even add value by grouping them into unit systems (the standard lists them alphabetically). Are there are any units or unit systems that you would like to see mentioned? Dondervogel 2 (talk) 21:59, 8 October 2017 (UTC)

Okay, so we should be fine under copyright. Off the top of my head, I would like to see common units not in SI, especially where there is some variation, where someone might want a "good" symbol, including kilowatt-hour, volt-amp, inch, foot, yard, chain, furlong, fathom, mile, knot, pound-force, pound-mass, kilogram-force/pond, slug, poundal, long ton, ounce (in its common variations), pint, quart, litre, pound per square inch, mile per gallon, troy ounce, mile per hour, minute, hour, year, atmosphere, bar, millimetre of mercury, astronomical unit, parsec, neper, shannon, natural unit of information. If there is, expressed in the document, a rationale/purpose for having the standard, a precis of this would be helpful. I think our focus should be on major modern use of units that the IEEE covers, not on regional (with the possible exception of the US!), obscure or limited use symbols or systems falling into disuse. May I ask what the order-of-magnitude size of the list is? —Quondum 00:55, 9 October 2017 (UTC)

The list comprises ~250 terms. It's main purpose is to provide a standard symbol for each unit. Some of the entries include definitions, especially where not defined by SI. The scope reads

This standard covers letter symbols[1] for units of measurement. It does not include abbreviations for technical terms, nor does it cover symbols for physical quantities.[2] The symbols given in this standard are intended for all applications, including use in text and equations; in graphs and diagrams; and on panels, labels, and nameplates. Provision is made for modifications to be used when only character sets of limited capability are available.

[1] “Letter symbol” as a technical term does not have the same meaning as either “name” or “abbreviation.” An abbreviation is a letter or a combination of letters that by convention represents a word or a name in a particular language. For example, the symbol for electromotive force is E , whereas the abbreviation is emf in English, fem in French, and EMK in German. The unit names ampere and second have sometimes been abbreviated amp and sec, respectively, but this usage is now deprecated. The standard unit symbols for ampere and second are A and s, respectively.

[2] As used in this standard, the term physical quantity means a measurable attribute of phenomena or matter. Examples are length, mass, and time.

Dondervogel 2 (talk) 08:05, 9 October 2017 (UTC)

Okay, I've tried to capture what it useful from this. We could still echo the emphasis on distinction between symbol and abbreviation. I hope the notation below (caret for power and 'e' for decimal exponent) are yours, and not theirs. Their list is short; it would be easy to repeat most of it, so I think we should consciously restrict the list here to symbols that could see use in multiple articles in WP. —Quondum 12:29, 9 October 2017 (UTC)

Yes, the shorthand exponential notation (both varieties) is mine, not theirs. Your assumption about the sort order is also correct. Dondervogel 2 (talk) 13:21, 9 October 2017 (UTC)

Phew! I had visions of my world getting turned upside down, with people reformatting articles to use the new "standard" notation (I have actually seen this in computer science articles, by someone claiming that the "outdated" notation no longer gets used!). Do you prefer the list form much like you have or a table? I might prefer the latter. I would have three four columns: name, symbol, definition/value, notes. I would be happy to do the reformatting from what you have provided. —Quondum 13:37, 9 October 2017 (UTC)

It would be easier to read if reformatted as a table. Be my guest! There's a case for maybe adding one more column, for abbreviations, if only to make the point that an abbreviation is not a symbol. Dondervogel 2 (talk) 18:18, 9 October 2017 (UTC)

If the standard lists abbreviations as well, then an additional column makes sense. However, if not, I would be inclined to make the point as a separate statement in the article, to the effect that the standard makes the point that an abbreviation is not a symbol. —Quondum 01:09, 10 October 2017 (UTC)

The standard does not include a separate column for abbreviations and I see your logic. We can include these in the notes column if that's your preference. I do think we need a clearer way of distinguishing between definitions and (potentially approximate) numerical values that fall short of a definition. Should we separate definition and value into separate columns, or is it sufficient to highlight the definitions with bold text, as now? Dondervogel 2 (talk) 07:16, 10 October 2017 (UTC)

... and another thing - for many of the units alternative unit symbols are provided for "limited character sets". For example if a character set is limited to only lower case (or upper case) the standard permits the alternative symbol "db" (or "DB") for the decibel, instead of "dB". Or if a character set does not include superscipts the standard permits "m3/s" as alternative to "m³/s". Or if Greek characters are not available the standard permits "uA" instead of "μA". Do you think these are worth a mention?

How would we include specific abbreviations anywhere, if the standard only makes a generic statement about them and does not give specific abbreviations? Maybe I'm misunderstanding you. If it does mention specific abbreviations for some, these can be added, and the 'notes' column might work best for these.

On the alternative symbols for use with limited character sets, these are probably worth giving, really useful in electronics: I see a lot of variation here (finding suitable way to express symbols is a challenging problem). If they are best given individually, then an additional column for these would work best. The alternative, with a predominantly generic prescription, might be best handled in a short section, e.g. that space not dot is used between multiplied units if raised dot not available, negative superscripts are made positive by use '/' and parentheses, positive superscripts are simply made regular characters, μ becomes u and Ω becomes [...], and upper and lower case are made into a single case with a limited set of exceptions (how to distinguish s and S, ua and μA, etc., or is it simply context?). [You may notice that I'm guessing: I have no idea what they say.]

Another stray thought: I seem to remember that there is an ISO standard with a similar objective. We should probably find and link to that as a "See also". —Quondum 12:30, 10 October 2017 (UTC)

* Abbreviations are given only occasionally, often to make a point about how not to use them. Example: "Although use of mph as an abbreviation is common, it should not be used as a symbol."

* I will first read the section on alternative symbols for limited character sets more carefully, and then return with a proposal (\Omega is replaced with "Ohm" btw). I believe much indeed relies on context.

* I'm not aware of an ISO standard with a similar goal. The closest I can think of is ISO 80000-3, which defines quantities and symbols for space and time (including, for example the year (symbol a), which it defines either as 365 d or 366 d, depending on context, and light year, for which there is no symbol - only the abbreviation "l.y.").

Dondervogel 2 (talk) 14:14, 10 October 2017 (UTC)

I read this as no attempt here by the standard to provide abbreviations, so the caution about these would stay in the notes column as we have it. I think the full ISO 80000 set might be what I was thinking of; maybe not the same goal, but includes most of this information. I'll link to it. —Quondum 03:25, 11 October 2017 (UTC)

I have reviewed the section on limited character sets. It's basically a set of rules explaining how to convert the standard symbols into one of several character sets with specified limitations. The specific character sets considered include ASCII, all lower case and all upper case. There is also consideration for HTML and email character sets, and for online representation of superscipts and subscripts. We could either summarize the rules or provide examples, or both. The standard includes a table with examples of 3 specific forms (referred to as "Form I" and "Form II", confusingly IMO given that there are 3 of them!). Selected examples from the table follow:

ampere

• Form I (mized case): A
• Form II (lc): a
• Form II (uc): A

candela per square meter

• Form I (mixed case): cd/m2
• Form II (lc): cd/m2
• Form II (uc): CD/M2

megohm

• Form I (mixed case): MOhm
• Form II (lc): mohm
• Form II (uc): MOHM

you get the drift. I see no attempt to disambiguate between mm and Mm in "Form II". Dondervogel 2 (talk) 13:53, 12 October 2017 (UTC)

List of units

Here's Quondum's wishlist, in the form <unit name [unit symbol; unit definition]. Notes> If it starts to become a comprehensive list (signficant proportional of whole) we need to watch out with the previously mentioned concern about copyright. Dondervogel 2 (talk) 15:08, 9 October 2017 (UTC)

Alphabetical list (incomplete)

• astronomical unit [ua; 1.495979×10¹¹ m]
• atmosphere, standard [atm; 101 325 Pa]
• atmosphere, technical [at; kgf/cm²]
• bar [bar; 100 kPa]
• foot [ft; 0.3048 m]
• hour [h; 60 min = 3600 s]
• inch [in; 2.54 cm]
• kilogram-force [kgf; 9.806 65 N]. Deprecated
• kilowatthour [kWh; 3.6 MJ]
• knot [kn; nmi/h]
• liter [L; 10⁻³ m³]. ... the letter symbol l is not recommended for US use ...
• mile (statute) [mi; 5280 ft = 1609 m]
• mile per hour [mi/h]. ... mph ... should not be used as a symbol
• millimeter of mercury [mmHg]. mmHg = 133.322 Pa; Deprecated
• minute (plane angle) [']
• minute (time) [min; 60 s]
• month [mo]
• neper [Np]. See Annex A for guidance concerning notation.
• ounce (avoirdupois) [oz; 1/16 lb = 28.350 g]
• pint [pt]. pt (Imp) = 0.568 26 L; pt (US dry) = 0.550 61 L; pt (US liquid) = 0.473 18 L
• pound (avoirdupois) [lb; 0.453 592 37 kg]
• pound-force (lbf]. lbf = 4.4482 N
• pound-force per square inch [lbf/in²]. ... the abbreviation psi ... should not be used as a symbol
• poundal [pdl; lb ft/s² = 0.1383 N]
• quart [qt]. qt (Imp) = 1.1365 L; qt (US dry) = 1.1012 L; qt (US liquid) = 0.946 35 L
• slug [slug; lbf s²/ft = 14.594 kg]
• ton (short) [ton; 2000 lb]
• voltampere [VA]
• watthour [Wh; 3.6 kJ]
• year [a]. Not uniquely defined

By type of unit

Units of mass

• unified atomic mass unit [u]. u = 1.660539×10⁻²⁷ kg; The (unified) atomic mass unit is defined as one-twelfth of the mass of an atom of the carbon-12 nuclide. Use of the old atomic mass unit (amu), defined by reference to oxygen, is deprecated (see IEEE/ASTM SI 10-2002)
• grain [gr; lb/7000]
• ounce (avoirdupois) [oz; 1/16 lb = 28.350 g]
• pound (avoirdupois) [lb; 0.453 592 37 kg]
• slug [slug; lbf s²/ft = 14.594 kg]
• ton (short) [ton; 2000 lb]
• metric ton [t; 1000 kg]
• ton, metric [t; 1000 kg]. Use of the name tonne for this unit is deprecated in the US (see IEEE/ASTM SI 10-2002).'

Units of distance

• mil [mil; 0.001 in]
• inch [in; 2.54 cm]
• foot [ft; 0.3048 m]
• mile (statute) [mi; 5280 ft = 1609 m]. mi := 5280 ft = 1609 m
• nautical mile [nmi; 1852 m]
• astronomical unit [ua]. ua = 1.495979×10¹¹ m

Units of time

• second (time) [s]. SI unit of time.
• minute (time) [min; 60 s]
• hour [h; 60 min = 3600 s]
• day [d; 24 h = 86 400 s]
• month [mo]
• year [a]. Not uniquely defined

Units of speed

• mile per hour [mi/h]. ... mph ... should not be used as a symbol
• knot [kn; nmi/h]

Units of volume

• pint [pt]. pt (Imp) = 0.568 26 L; pt (US dry) = 0.550 61 L; pt (US liquid) = 0.473 18 L
• liter [L; 10⁻³ m³]. ... the letter symbol l is not recommended for US use ...
• quart [qt]. qt (Imp) = 1.1365 L; qt (US dry) = 1.1012 L; qt (US liquid) = 0.946 35 L
• gallon [gal; 231 in³]. gal (Imp) = 4.5461 L; gal (US) := 231 in³ = 3.7854 L

Units of force

• poundal [pdl; lb ft/s² = 0.1383 N]
• pound-force [lbf]. lbf = 4.4482 N
• kilogram-force [kgf; 9.806 65 N]. Deprecated

Units of pressure

• millimeter of mercury [mmHg]. mmHg = 133.322 Pa; Deprecated
• inch of water [inH₂O]. inH₂O = 249.09 Pa
• foot of water [ftH₂O]. ftH₂O = 2989.1 Pa
• inch of mercury [inHg]. inHg = 3386.4 Pa
• pound-force per square inch [lbf/in²]. ... the abbreviation psi ... should not be used as a symbol
• atmosphere, technical [at; kgf/cm²]
• bar [bar; 100 kPa]
• atmosphere, standard [atm; 101 325 Pa]

Units of power

• voltampere [VA]
• var [var]. IEC name and symbol for the SI unit of reactive power.
• horsepower [hp]. Use of the SI unit of power, the watt, is preferred.

Units of energy

• electronvolt [eV]. eV = 1.602 176 × 10^–19 J
• erg [erg; 10⁻⁷ J]
• calorie (thermochemical) [cal_th; 4.184 J]. Deprecated
• calorie (International Table) [cal_IT; 4.1868 J]. Deprecated
• British thermal unit (thermochemical) [Btu_th]. Btu_th = 1054.350 J
• British thermal unit (International Table) [Btu_IT]. Btu_IT = 1055.056 J
• watthour [Wh; 3.6 kJ]
• calorie (nutrition) [kcal; 4184 J].
• kilowatthour [kWh; 3.6 MJ]
• therm [thm; 1.000×10⁵ Btu]

Units of information storage

• bit [b]
• byte [B]
• octet [o]
• kilobyte [kB; 1000 bytes]
• kibibyte [KiB; 2¹⁰ B = 1024 B]
• megabyte [MB; 1 000 000 bytes]
• mebibyte [MiB; 2²⁰ B = 1 048 576 B]
• gigabyte [GB; 10⁹ B]
• gibibyte [GiB; 2³⁰ B = 1 073 741 824 B]

Units of level

• decibel [dB]. See Annex A for guidance concerning notation.
• bel [B]. See Annex A for guidance concerning notation.
• neper [Np]. See Annex A for guidance concerning notation.

Units of angle

• second (plane angle) [″]
• minute (plane angle) [′]
• radian [rad]

Other units (alphabetical order)

• baud [Bd]
• bit per second [b/s]
• curie [Ci; 3.7e10 Bq]
• rad [rad; 0.01 Gy]
• rem [rem; 0.01 Sv]
• revolution per minute [r/min]. rpm ... should not be used as a symbol.

Statement qualifying notes column (verbatim)

The notes give exact definitions (indicated by the symbol :=) for many of the units and give conversion factors in other cases. The conversion factors indicated with the equals sign are accurate to the number of figures shown. For more accurate conversion factors and other general information about units, see IEE/ASTM SI 10-2002.

Annex A, entitled 'Notation for expressing the reference of a level'

Annex A opens with a statement of the generic form for expressing levels. That sentence is followed by some examples.

Opening sentence (verbatim)

The level representing a physical quantity x with a reference quantity x_ref may be indicated by

L_x(re x_ref) or by L_x/xref

Selected examples

1. L_I(re 1 A) = −10 Np
2. L_p(re 20 μPa) = 15 dB
3. L_{p/(20 uPa)} = 15 dB

Example 1 means the level of an electric current is 10 Np below 1 A. Examples 2 and 3 have identical meaning. In both cases the sound pressure level is 15 dB above 20 μPa.

Table form

Except where stated otherwise, individual tables are sorted in order of increasing unit magnitude

Table for mass

Units of mass
Name	Symbol	Definition	Value	Notes
unified atomic mass unit	u		1.660539×10−27 kg
grain	gr	lb/7000	0.00006479891 kg
ounce (avoirdupois)	oz	1/16 lb	28.350 g 0.028349523125 kg
pound (avoirdupois)	lb	0.45359237 kg	0.45359237 kg
kilogram	kg		1 kg	SI unit of mass.
slug	slug	lbf⋅s2/ft	14.594 kg	[Using the British standard definition of lbf = gn⋅lb, 1 slug = 14.5939029372... kg.]
ton (short)	ton	2000 lb	907.18474 kg
ton, metric	t	1000 kg	1000 kg	Use of the name tonne for this unit is deprecated in the US. [Appears also in a separate entry in the standard as "metric ton".]

Table for distance

Units of distance
Name	Symbol	Definition	Value	Notes
Ångström	Å	10−10 m	0.000 000 0001 m	Deprecated (see IEEE/ASTM SI 10-2002).
millimicron	nm		0.000 000 001 m	Use of the name millimicron for the nanometer is deprecated.
micron	μm		0.000 001 m	The name micron is deprecated. Use micrometer.
mil	mil	0.001 in	0.000 0254 m
inch	in	2.54 cm	0.0254 m
foot	ft	0.3048 m	0.3048 m
yard	yd	0.9144 m	0.9144 m
meter	m		1 m	SI unit of length.
mile (statute)	mi	5280 ft	1609 m 1609.344 m
nautical mile	nmi	1852 m	1852 m
astronomical unit	ua		1.495979×1011 m

Table for time

Units of time
Name	Symbol	Definition	Value	Notes
second (time)	s		1 s	SI unit of time.
minute (time)	min	60 s	60 s	Time may also be designated by means of superscripts as in the following example: 9h 46m 30s.
hour	h	60 min	3600 s
day	d	24 h	86 400 s
month	mo			Not uniquely defined.
year	a			Not uniquely defined.

Table for speed

Units of speed
Name	Symbol	Definition	Value	Notes
foot per minute	ft/min		0.00508 m/s
inch per second	in/s		0.0254 m/s
foot per second	ft/s		0.3048 m/s
mile per hour	mi/h		0.44704 m/s	Although use of mph as an abbreviation is common, it should not be used as a symbol.
knot	kn	nmi/h	0.514 m/s	[Note recurring decimal 0.51444...]
meter per second	m/s		1 m/s	SI unit of speed.

Table for volume

Units of volume
Name	Symbol	Definition	Value	Notes
cubic inch	in3		0.004162314256 L
pint	pt		pt (Imp) = 0.56826 L	[Exact value is 0.56826125 L.]
			pt (US dry) = 0.55061 L	[Exact value is 0.5506104713575 L. ]
			pt (US liquid) = 0.47318 L	[Exact value is 0.473176473 L.]
liter	L	10−3 m3	1 L	In 1979, the CGPM approved L and l as alternative symbols for the liter. Because of frequent confusion with the numeral 1, the letter symbol l is not recommended for US use (see Federal Register notice of July 28, 1998, vol. 63, no. 144, p. 40334). The script ℓ shall not be used as a symbol for liter. [Shares symbol with lambert ]
quart	qt		qt (Imp) = 1.1365 L	[Exact value is 1.1365225 L.]
			qt (US dry) = 1.1012 L	[Exact value is 1.101220942715 L.]
			qt (US liquid) = 0.94635 L	[Exact value is 0.946352946 L.]
gallon	gal		gal (Imp) = 4.5461 L	[Exact value is 4.54609 L.]
		231 in3	gal (US) = 3.7854 L 3.785411784 L
cubic foot	ft3		28.316846592 L
barrel	bbl	42 gal US	158.99 L 158.987294928 L	This is the standard barrel used for petroleum and petroleum products. Different standard barrels are used for other commodities.
cubic yard	yd3		764.554857984 L
cubic meter	m3		1000 L	SI unit of volume.

Table for force

Units of force
Name	Symbol	Definition	Value	Notes
dyne	dyn	10−5 N	0.000 01 N	Deprecated (see IEEE/ASTM SI 10-2002).
poundal	pdl	lb⋅ft/s2	0.1383 N 0.138254954376 N
newton	N		1 N	SI unit of force.
pound-force	lbf		4.4482 N
kilogram-force	kgf	9.80665 N	9.80665 N	Deprecated (see IEEE/ASTM SI 10-2002). [9.80665 N = 1 kg × 9.80665 m/s2]

Table for pressure

Units of pressure
Name	Symbol	Definition	Value	Notes
pascal	Pa		1 Pa	SI unit of pressure.
millibar	mbar		100 Pa	[1 mbar = 100 kPa/1000 = 100 Pa]
millimeter of mercury	mmHg		133.322 Pa	Deprecated (see IEEE/ASTM SI 10-2002).
inch of water	inH2O		249.09 Pa	(ISO)
foot of water	ftH2O		2989.1 Pa	(ISO)
inch of mercury	inHg		3386.4 Pa	(ISO)
pound-force per square inch	lbf/in2			Although use of the abbreviation psi is common, it should not be used as a symbol.
atmosphere, technical	at	kgf/cm2	98066.5 Pa	Deprecated (see IEEE/ASTM SI 10-2002).
bar	bar	100 kPa	100000 Pa	Deprecated (see IEEE/ASTM SI 10-2002).
atmosphere, standard	atm	101325 Pa	101325 Pa	Deprecated (see IEEE/ASTM SI 10-2002).

Table for power

Units of power
Name	Symbol	Definition	Value	Notes
watt	W		1 kg⋅m2⋅s−3	SI unit of power.
voltampere	VA		1 kg⋅m2⋅s−3	IEC name and symbol for the SI unit of apparent power.
var	var		1 kg⋅m2⋅s−3	IEC name and symbol for the SI unit of reactive power.
horsepower	hp			Use of the SI unit of power, the watt, is preferred.

Table for energy

Units of energy
Name	Symbol	Definition	Value	Notes
electronvolt	eV		1.602176×10−19 J	Experimentally determined unit of energy accepted for use with the SI.
erg	erg	10−7 J	0.000 0001 J	Deprecated (see IEEE/ASTM SI 10-2002).
joule	J		1 kg⋅m2⋅s−2	SI unit of energy, work, and quantity of heat.
newton meter	N⋅m		1 kg⋅m2⋅s−2	SI unit of torque (moment of force) or of work or energy. When referring to energy, the joule is normally used: J := N⋅m.
foot pound-force	ft⋅lbf			[unit of energy]
pound-force foot	lbf⋅ft			[lbf⋅ft ≈ 4.4482 N × 0.3048 m ≈ 1.3558 N⋅m; unit of torque]
calorie (thermochemical)	calth	4.184 J	4.184 J	Deprecated (see IEEE/ASTM SI 10-2002).
calorie (International Table)	calIT	4.1868 J	4.1868 J	Deprecated (see IEEE/ASTM SI 10-2002).
British thermal unit (thermochemical)	Btuth		1054.350 J
British thermal unit (International Table)	BtuIT		1055.056 J
watthour	Wh	3.6 kJ	3.6 kJ
calorie (nutrition)	kcal	4184 J	4.184 kJ
kilowatthour	kWh	3.6 MJ	3600 kJ
therm	thm		1.000×105 Btu	[The standard does not specify whether BtuIT or Btuth is intended.]

Table for information

Units of information storage
Name	Symbol	Definition	Value	Notes
bit	b		1 bit	In information theory, the bit is a unit of information content equal to the information content of a message, the a priori probability of which is one-half. In computer science, the name bit is used as a short form of binary digit.
octet	o		8 bit	An octet is a string of eight bits, operated on as a unit.
byte	B		1 B	A byte is a string of bits, usually eight bits long, operated on as a unit. A byte is capable of holding one character in the local character set. [Shares symbol with bel.]
kilobyte	kB	1000 bytes	1000 B	1 kB = 1000 B
kibibyte	KiB	210 B	1024 B	1 KiB = 1024 B
megabyte	MB	1 000 000 bytes	1000000 B	1 MB = 1000 kB
mebibyte	MiB	220 B	1048576 B	1 MiB = 1024 KiB
gigabyte	GB	109 B	1000000000 B	1 GB = 1000 MB
gibibyte	GiB	230 B	1073741824 B	1 GiB = 1024 MiB

Table for level

Units of level
Name	Symbol	Definition	Value	Notes
decibel	dB		1 dB	See Annex A for guidance concerning notation.
neper	Np			See Annex A for guidance concerning notation.
bel	B		10 dB	See Annex A for guidance concerning notation. [Shares symbol with byte.]

Table for angle

Units of angle
Name	Symbol	Definition	Value	Notes
second (plane angle)	″			[Exact value is (1/60)′.]
minute (plane angle)	′			[Exact value is (1/60)°.]
minute (plane angle)	°			[Exact value is 180/π rad.]
radian	rad		1 rad	[Shares symbol with rad.]

Table for other quantities, in alphabetical order

Other units
Name	Symbol	Definition	Value	Notes
baud	Bd			In telecommunications, a unit of signaling speed equal to one element per second.
bit per second	b/s		1 bit/s
curie	Ci	3.7×1010 Bq		A unit of activity of a radionuclide. Use of the SI unit, the becquerel, is preferred.
lambert	L			[Shares symbol with liter.]
rad	rad	0.01 Gy		A unit of absorbed dose in the field of radiation dosimetry. Use of the SI unit, the gray, is preferred. [Shares symbol with radian.]
rem	rem	0.01 Sv		A unit of dose equivalent in the field of radiation dosimetry. Use of the SI unit, the sievert, is preferred.
revolution per minute	r/min			Although use of rpm as an abbreviation is common, it should not be used as a symbol.

Discussion

I like the organization by quantity (not really "subject"). And yes, the alphabetical list is not needed. One question: is the symbol they use for minute of arc an apostrophe or a prime? I tend to prefer the latter. I guess we should have second of arc (probably "second (plane angle)") as well. —Quondum 15:29, 9 October 2017 (UTC)

I added both varieties of second. The symbols used for minute, second of angle are a single and double prime, respectively. Dondervogel 2 (talk) 20:31, 9 October 2017 (UTC)

See what you think of the table. I find the italics in the third column problematic, and would be inclined to remove them, using the bold to indicate definition and non-bold to indicate information. Several of the values are inexact, and I would take the editorial liberty to substitute '≈' for '='. —Quondum 00:49, 10 October 2017 (UTC)

Are the shannon and nat not mentioned in the standard? —Quondum 01:05, 10 October 2017 (UTC)

Seems not. At least not in the obvious places. The lists go from nanosecond to nautical mile and from second (time) to siemens. A scan for the sequences "nat" and "shannon" also revealed nothing. Dondervogel 2 (talk) 07:12, 10 October 2017 (UTC)

Er ... what do you mean by "might be exact"? It is easy to verify that the values given are not exact (there are . Okay, so you seem to want this as an extract (in the sense of directly quoting the source rather than a paraphrase). I'm fine with this, though I'll note that the MOS seems to prefer the contrary. I would at least be inclined to sensitize the reader that presenting the content has been given priority over the evident intent and accuracy of what is presented. We should also take care to include what contextual caveats are given; for example, what they say about precision in what is presented as equalities. In a reference (i.e. WP), we would not want an incautious reader to blindly take the 'equalities' as being exact. —Quondum 02:32, 12 October 2017 (UTC)

A simple example to illustrate my point is the kibibyte. This unit is defined according to the standard as 2^10 bytes. It is also equal to 1024 bytes but is not defined that way. Similarly a numerical value is provided for the pound-force expressed in newtons, except without a definition. Who are we to say whether this quantity of newtons is exact or approximate? For this reason I prefer to state "lbf = 4.4482 N", precisly as stated in the standard, without implying this is a definition (it's not) but also without implying it's an approximation (it might be or it might not - we just don't know). Dondervogel 2 (talk) 11:02, 12 October 2017 (UTC)

Re your other point about direct quote vs paraphrase, I don't mind which we end up with, but if we go for paraphrase I prefer to discuss how best to do so first. How about we start with the direct quotes (as now) and take it from there? Dondervogel 2 (talk) 11:44, 12 October 2017 (UTC)

I'm happy to stay with quotes at this stage. Especially since I prefer not to be discussing too many points at once.

On the precision, I'm tempted to rather strongly assert that it is IEEE's clear intent, in the non-bold figures, to provide a "sufficiently precise" working figure that also serves to disambiguate interpretations. They have clearly chosen 4 to 5 five significant figures. That is, they are using the convention that precision is given by the number of digits. In this WP context, however, leaving the reader to make this (IMO unambiguous) inference is, I would suggest, ignoring the range of types of reader, and the load of disambiguation that it places on them. The mile as 1609 m is a clear example; I expect that IEEE would be horrified/amused if anyone was daft enough to use that figure if anything more precise was needed – the error is about 0.2 mm per metre (or 1 ft per mile). The accurate figure is 1609.344 m, and that is possibly the only figure in any modern definition (though usually this is derived from a different defined ratio, e.g. ft/m). This section, for example, is utterly misleading. IEEE does not specify that figure, and it is just wrong as a standalone statement. I think we should state the very clear intent in the text with the table: that the figures not in bold are not precise, so that the reader does not have to do as I did: cross-check every figure in the table to determine the convention being used in the presentation of the figures. —Quondum 13:09, 12 October 2017 (UTC)

I agree partly. But then again not quite. I think some are precise and some not. To the extent that the intent seemed obvious to me I have included the text "precise" or "approximate" in the notes column (but not in italics so we know it's our words, not theirs). Do we agree so far? Dondervogel 2 (talk) 14:57, 12 October 2017 (UTC)

I think that we have established that the figures not in bold are not to be regarded as anything but informative. We do not need to make any statement, but as a priority should avoid misleading the incautious reader into thinking something informative is normative. What would you think of simply omitting the non-bold figures? The true value of this article will be in the information about what symbols are listed. —Quondum 00:54, 18 October 2017 (UTC)

I would be prefer to keep them in the table but to clearly distinguish them from the definitions, which is why I was careful to italicize the notes that were clearly not part of the definitions. My suggestion to achieve this is to create two different columns, one containing the definitions and another containing numerical values, some of which follow from the definitions while others are just stated as empirical "facts". Dondervogel 2 (talk) 08:26, 18 October 2017 (UTC)

I'll note that the inexact figure for mile was not italicized – was this overlooked?

Adding a column for non-definition values could work. An extra column means that the table gets quite wide, but we can debate the utility of this separately. My problem is that the reader might be misled by a table repeated from a "standard" without some guidance that they should not be regarded as exact. That is why I was asking for any clarifying statement about the nature of these figures that might be in the IEEE 260.1 document and which we could use. Or we could add our exact values as a footnote to each non-definition value, with "not necessarily exact" for those that we have not found the exact value for. The Btu figures and depth-of-liquid values are almost certainly inexact, but may be difficult to find exact figures for. If we simply have a column headed "Value", with no qualification, footnote or other indication, the incautious reader might assume that it is a value mandated by the standard, and I would call this misrepresentation.

We could move the non-definition figures into the notes column, which would mostly avoid wasting space, and hint at the non-definition nature. We can still consider including notes about figures giving more exact information, but it becomes less imperative. —Quondum 12:16, 18 October 2017 (UTC)

I added a direct quotation for the statute mile to clarify. The notes column is qualified by the statement "The notes give exact definitions (indicated by the symbol :=) for many of the units and give conversion factors in other cases. The conversion factors indicated with the equals sign are accurate to the number of figures shown. For more accurate conversion factors and other general information about units, see IEE/ASTM SI 10-2002." Dondervogel 2 (talk) 19:35, 18 October 2017 (UTC)

If we had a "value" column we could populate it with conversions to SI units, making the progression from small to large more intuitive. Dondervogel 2 (talk) 21:54, 18 October 2017 (UTC)

Okay, I've split out the value column. I like the clarification about accuracy that you have given here; we can use that almost verbatim as a note at the bottom of the table. —Quondum 00:32, 19 October 2017 (UTC)

Thank you. That makes the table clearer IMO. I added the note about accuracy in the same way as it appears in the standard. Corollary: now that definitions have their own column, the bold type no longer serves a useful purpose. Can it be removed? Dondervogel 2 (talk) 07:52, 19 October 2017 (UTC)

It certainly makes it easier to work with and consider the detail. The bold does seem unnecessary now, so I've removed it. Indication of (in)exactness in the value column is something still to consider; for now I've used italics to distinguish. There are a few atypical definitions; for example, I would have expected "1.000 × 10⁷ Btu" to read "simply "10⁷ Btu", and "1 000 000 bytes" to read "10⁶ B", in line with the pattern of most of the rest. —Quondum 10:55, 19 October 2017 (UTC)

An afterthought: the use of "1 W" and "1 J" for var, VA and newton-meter possibly only serves to confuse things: while from a pure SI dimensional analysis perspective this is correct, it flies in the face of convention. Do they actually mention these values with these forms of the units in the standard? —Quondum 11:01, 19 October 2017 (UTC)

Couple reactions

* I checked the definitions of thm and MB and have edited the table accordingly

* I understand your concern about stating "1 W" and "1 J" as values for the units you mention. These are not given by the standard but I wanted a way of showing that it's not only the dimensions that are the same but also the magnitude. My suggested solution is to leave these numerical values and add a disclaimer in the notes column. Alternative suggestions for getting this message across are invited.

Dondervogel 2 (talk) 12:09, 19 October 2017 (UTC)

I imagine that the usual way to do this would be to put var = 1 V·A, VA = 1 V·A, and N·m = 1 N·m. This seems to achieve what you want without jarring the sensibilities of electrical and mechanical engineers, with no disclaimer needed. The latter case is somewhat tautological, but only if the left-hand side is treated as a product rather than as a monolithic unit. If the reader starts by thinking of it as a product of two units (since that is what the notation suggests), no explanation is needed. —Quondum 12:41, 19 October 2017 (UTC)

I made a proposal for N m (cf J). See what you think. If you like it we can try something similar for the VA and var (cf W). Dondervogel 2 (talk) 13:51, 19 October 2017 (UTC)

It works, I think. Though considering the other functions that the column serves (e.g. ordering by magnitude), I think perhaps I've been getting overly pedantic. In the normal engineering context, one communicates meaning in the choice of otherwise equivalent units (e.g. W vs. VA vs. var, and J vs. N⋅m). Here, I guess one cannot avoid blurring the lines, because we are talking about units rather than using them. In fact, the VA and var issues become more acute (in the engineering context rather than here) because of the complexity of what "reactive power" really is. —Quondum 22:57, 19 October 2017 (UTC)

It's fine like it is. In fact the table is nearly ready to be included in the article. IMO we just need a better way of distinguishing between exact and approximate values in the values column. How about an asterisk to denote exact values? Dondervogel 2 (talk) 04:27, 20 October 2017 (UTC)

The convention that I've seen in such tables on WP for distinguishing exact values is to bold the exact values and to put a note on the table to that effect. An asterisk does not work too well for me: it usually denotes a caveat. Thus, if we were to use asterisks (or preferably a footnote tag), it should be on the inexact (and unknown exactness) values. Which brings me to notes column: it still needs similar review (we currently have an italic/nonitalic convention that we are using as editors, but would have to be clarified explicitly, possibly changed to something else). There is also redundant info here. For example, all the "inexact" comments would be redundant once inexact values are tagged. Also, the existing superscripts 'a' and 'b' should be turned into hyperlinks – easy with square brackets (e.g. (ISO)^[b]) but I'd have to find how to do it without the brackets if you prefer that. —Quondum 12:14, 20 October 2017 (UTC)

In reply to your implied questions

• indication of exact values: I have no objection to use of bold type for this
• notes column: I agree this needs tidying up, along the lines you suggest
• notes a and b: I have no objection to use of brackets

Dondervogel 2 (talk) 12:27, 20 October 2017 (UTC)

What would you think of swapping italics and non-italics in the 'Notes' column? It would reflect the source, and would allow us to capture the italics used in the entry for bit. —Quondum 03:44, 21 October 2017 (UTC)

I'm not sure. Or rather, I do not object to your improving the formatting (the changes you've made so far have all resulted in improvements and I've no reason to doubt this one will too). The only condition (and I can tell from your careful edits that you're already aware of the need for this) is to retain the information about the origin of the information, and in particular to distinguish between values provided by the standard and those obtained from other sources. What we have now are

* Exact values provided directly by the standard (definitions; values)

* Exact values that we have derived from information provided by the standard (values)

* Exact values that we have derived from other sources (notes, presently distinguished by explicit statement "exact value" or similar)

* Approximate values provided by the standard (values)

* Approximate values that we have derived from the inforation provided by the standard (are there examples of this?)

* Approximate values that we have derived from other sources (notes)

Have I got this right so far? Dondervogel 2 (talk) 09:02, 21 October 2017 (UTC)

I think it is very helpful to use these categories explicitly, so I've made this a little more explicit in the footnotes.

• There are presently several examples that fit into your second category (exact values derived directly from the standard) that are not presently in the 'Values' column, including grain, ounce, mile, ton (short), mile (statute), mile per hour, poundal, gallon (US), quart (US liquid), pint (US liquid). The barrel can also have an exact value determined from its definition as 42 gal (US). I think, where appropriate, that bold and an italic figures can be given in the same entry.
• The values for the units of angle are universally known, but do not appear to be given in the standard; maybe these belong under "Exact values that we have derived from other sources"?
• With only the reasonable presumption of standard gravity for relating pound and pound-force (as clearly is true of kilogram and kilogram-force), we can derive exact values from the standard for others: lbf, lbf/in², lbf⋅ft. The presumption could be handled via a footnote.
• I do not think that we have examples here where we have derived non-exact values from information provided by the standard. I would prefer to restrict these to presenting exactly the approximate values that are presented in the standard (i.e. the category that you list above it), unless such a restriction proves awkward.

—Quondum 15:08, 21 October 2017 (UTC)

Happy with all your suggestions except use of standard gravity to derive lbf and related units. I would prefer to make the opposite statement (that it is defined as a weight, which depends on latitude and therefore ambiguous). Dondervogel 2 (talk) 15:41, 21 October 2017 (UTC)

Also, I'd quite like to split the single monolithic table into multiple small ones (decreases risk of edit conflict and makes it less unwieldy). Don't know how though so I'm hoping you will offer to do this :P Dondervogel 2 (talk) 15:48, 21 October 2017 (UTC)

Yep, no problem, I'll take care of this. I was thinking along these lines too. —Quondum 21:24, 21 October 2017 (UTC)

Value of lbf

According to the psi talk page there's a British standard that defines the lbf in terms of the standard gravity value of 9.80665 m/s2. Dondervogel 2 (talk) 19:08, 21 October 2017 (UTC)

... and the BSI standard is now used as a source from the lbf article. A lot can change in 40 years (the standard is dated 1974!) but on the other hand, what would be the reason for redefining the pound-force? Unless someone comes up with evidence to the contrary, this seems good enough to me to accept the definition of lbf as lb*g_std. Dondervogel 2 (talk) 20:09, 21 October 2017 (UTC)

I was never in doubt of this, or that IEEE Std 260.1-2004 relied on it. All the approximate figures that it gives are consistent with it, and this exact figure corresponds to the definition of kgf. My problem is that the IEEE standard simply fails to define lbf. We are consequently technically forced to fall back on "outside references" for its definition, such as the standard you mention. Which also means we cannot put the known-to-be-exact values in the 'Value' column where they would belong! In contrast, many of the exact figures can be traced to the document itself. —Quondum 22:04, 21 October 2017 (UTC)

Aargh! My brain short-circuits every time I try to think through these units, because it seems so circular. The definition of the slug is in terms of the lbf, which is defined in terms of the lb – at least in the precise and modern world, where we are trying to retrospectively assign accurate or even exact values to old units with respect to a well-understood system. However, this logic simply does not work: defining one mass unit (slug) in terms of another (lb) could not have been the logic in a metrologists's mind when defining a slug. So, the lbf was some reference force (e.g. the gravitational force on a reference object at a specified geographic location, but it could in principle have been any force reference). And the non-coherent lb-lbf-ft-s system probably was never formalized as a system. Anyhow, this is a roundabout way of saying that the lbf could never, other than once it was defunct, have had an "exact" value, just as with the kgf. So I think that the best that we can do is in effect say that "the only exact figure that could have been given to the lbf is lbf = g_n × lb = 9.80665 m/s² × 0.45359237 kg, as has been done by the BSI". IEEE Std 260.1-2004 does not reference the BSI, but references ISO 31-3 (superseded by ISO 80000-4). We should not be putting BSI's words into IEEE's mouth, but maybe we could hope to find someone with access to ISO 31-3? I seem to remember a group on WP was mentioned who might do this kind of specific reference. Until then, perhaps we should remain silent about exact values determined by lbf, as was the IEEE. —Quondum 03:51, 22 October 2017 (UTC)

I have no objection to holding back (because I agree it's a troublesome unit, whose definition is unclear), but I don't really understand your caution for this unit compared with (say) the astronomical unit. You could equally argue that it was not the intention of astronomers to define this unit in terms of the metre - it was just the distance to the Sun. I'm sure we could find alternative definitions to that of the IAU, but here we cite IAU even though IEEE does not. Why not use the BSI value for lbf and just state that we've done so, following the same reasoning? Or should we instead (for consistency) remove the IAU definition of the ua? Dondervogel 2 (talk) 07:50, 22 October 2017 (UTC)

IMO, the value of providing exact values here is to emphasize the inexactness of the provided values, and secondarily to suggest that the exact values are probably what the authors had in mind when they rounded them (and maybe also to suggest that exact values can be found). However, since the nature of the inexactness has now been clarified in the footnote of the value column, externally sourced values (u, slug, ua, lbf, etc.) are probably best removed. My initial motivation in compiling these was to convince you that no exactness outside of definitions should be assumed, since you appeared to be putting too much weight on the approximate values listed in the standard. In the process, I have been quite surprised to see quite how many values can be determined exactly from this document with no other reference, and went off on a bit of a mission doing so comprehensively. In the end, the primary value of this standard is (only) as a reference for unit symbols not provided by in ISO 80000. —Quondum 02:09, 24 October 2017 (UTC)

I see two possible replies to this, depending on the context, so I offer both:

1. In the context of this article, with its present scope, it is best to remove all exact values except those provided as definitions by the standard itself. We should avoid mention in this article of (for example) the exact values of the ua, lbf and related units.
2. In the wider context of our mutual aim to make these symbols available more widely, it is best to combine information from multiple sources, in which case it would become legitimate to specificy exact values of ua, lbf etc. Doing so would inevitably reveal inconsistencies between the various sources, which is a valuable end in its own right. I agree with the anonymous editor that doing so goes beyond the scope of this article.

I conclude we should resume the discussion of point 2 elsewhere. Where though? Dondervogel 2 (talk) 06:23, 24 October 2017 (UTC)

I guess, given the recent discussions and the lack of an obvious place, my inclination would be simply to edit in the useful reference information from this source as it pertains to each symbol into the relevant article on the unit. However, extracting the information from the standard into a single place towards that goal has been useful. Though as I've hinted, I do not feel compelled to complete that process at any particular pace. My inserting the information in any article is usually driven by my noticing the omission there, at which point I'd fetch it (and would previously have been stymied for lack of a source). At least now I have managed to get access to a copy of the standard as well, which negates my personal need for capturing a list. If we do move this to main space, I agree with your assessment in your first point. I must confess, I have not really thought of this as an article per say at any stage, but rather as useful information (and as a fun exercise). —Quondum 12:00, 24 October 2017 (UTC)

An afterthought: this standard does not pretend to define any units or values; IMO it only gives these for clarity. As such, any specific information in mainspace would really only include name, symbol and a note when deprecated. Which is to say, the definition and value columns could be removed entirely. But you might object :-) —Quondum 12:08, 24 October 2017 (UTC)

Why?

Why are there massive lists of units on this talk page? Have editors drifted into thinking that the information in a source should be extracted and provided in an article about that source? This is not how Wikipedia or any other encyclopedia proceeds. Instead, we use a source such as this in articles as appropriate, for example in Pound (force) to provide and reference the letter symbol. We do not extract the tables in Kaye and Laby, Perry's Chemical Engineers' Handbook, the CRC Handbook of Chemistry and Physics or IUPAC's Quantities, Units and Symbols in Physical Chemistry into those articles; we use them as sources elsewhere. We have an article on the International System of Units, not the BIPM brochure. We explain what ISO 9000 covers, briefly abstract its core principles and subject headings, and discuss its consequences; we do not paraphrase every paragraph. Our articles on the Oxford English Dictionary and Webster's Dictionary don't list all the words in them. So what's going on here? 92.19.24.9 (talk) 11:07, 22 October 2017 (UTC)

The main purpose of the standard is to provide letter symbols for a variety of units, including many outside the International System of Quantities (ISQ); the standard also provides definitions of the units and additional information about the units. The main purpose of this article is to describe the standard. The table on this talk page provides those letter symbols and definitions to WP readers, with a focus on those outside the ISQ; in particular we have refrained from providing information about SI units, precisely because there is ample information about these units elsewhere on WP. If you can suggest a better way of providing this information about non-ISQ units to WP readers, please feel free to do so. Dondervogel 2 (talk) 11:23, 22 October 2017 (UTC)

Provide it in the individual articles about the units, where it will be useful and where users will find it, according to normal Wikipedia practice. 92.19.24.9 (talk) 11:52, 22 October 2017 (UTC)

BTW, I'm struggling to see in the above tables any units which measure quantities that are not part of the International System of Quantities. Taking those section headings above, mass, distance, time, speed, volume, force, pressure, power, energy, information in various aspects, sound level, angle and others are all members of the ISQ and some are even base quantities. But that's a red herring. "The main purpose of this article is to describe the standard" and that has already been done. The tables above do not describe the standard. 92.19.24.9 (talk) 12:26, 22 October 2017 (UTC)

I'll address the "red herring" first, using volume as an example. In its present form that table comprises 6 units, of which 4 are outside the ISQ. The litre and cubic metre are included to provide context. Addressing your main point, the present WP article provides a summary of the standard, which in my opinion can usefully be expanded. There is nothing to stop you or any other editor using the same information in the articles about individual units, or unit systems. What do others think? Dondervogel 2 (talk) 12:48, 22 October 2017 (UTC)

You're confusing the ISQ with SI. Volume is a quantity in the ISQ. The cubic metre is an SI unit. I look forward to seeing what other editors think and would be interested to hear why this standard should be treated differently from the sources I mention above. 92.19.24.9 (talk) 13:08, 22 October 2017 (UTC)

The cubic metre is indeed an SI unit, and the litre is a non-SI unit accepted for use alongside the SI. Both are part of the ISQ, while the pint, quart, gallon and barrel (in their various forms) are not. Where is the confusion? Dondervogel 2 (talk) 13:15, 22 October 2017 (UTC)

No, volume is part of the International System of Quantities. The cubic metre and the litre are not part of the ISQ. They're units of measurement. Units are used in measuring quantities, they are not themselves quantities and they are not part of the International System of Quantities, whether they're SI units or not. Our own article on the ISQ is clear: "The International System of Quantities (ISQ) is a system based on seven base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. Other quantities such as area, pressure, and electrical resistance are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with the SI units[1] and also includes many other quantities in modern science and technology.[2]" 92.19.24.9 (talk) 13:38, 22 October 2017 (UTC)

OK, I understand your point better now, which was indeed a red herring. What I meant when I said "ISQ" was the collection of quantities and units defined by ISO/IEC 80000. My point is that ISO/IEC 80000 goes to a lot of trouble to provide definitions and unit symbols for those units that are defined by ISO/IEC 80000. It does not so for units that are not defined by ISO/IEC 80000, including Imperical units and US customary units. Our main purpose (or at least mine) in embarking on the venture whose utility you are questioning was to provide a list of international standard unit symbols for such units, supplemented by definitions and related information where supported by IEEE 260.1.

First, thank you for the clarification. The confusion lay in equating the ISQ with ISO/IEC 80000, a standard which documents the ISQ but is not the ISQ. Not everything mentioned in ISO/IEC 80000 is part of the ISQ; the units, for example, are not. However, this confusion points to one way forward, as do your last words.

You wish to provide a List of international symbols for units outside SI. In creating that, you would be writing about your actual subject rather than about one example of documentation of your subject. Various sources would be available for that article, IEEE 260.1 among them. This article has only one source, which is the subject of the article and in no sense independent of it, and no sources for or assertions of notability. I do recommend reviewing Wikipedia:Notability with this current article in mind; you may be driven to the conclusion that the subject of the current article does not pass the notability test and the article would fail nomination at WP:AfD. Yes, List of international symbols for units outside SI would also be open to challenge; that does take us back to the view that in possessing a copy of IEEE 260.1, you possess a useful reference for the letter symbols provided in our articles on units of measurement. 92.19.24.9 (talk) 18:16, 22 October 2017 (UTC)

I confess that possibility had not occurred to me. Thank you for the suggestion. As I have been working collaboratively with Quondum I shall await his or her reaction before deciding what to do. Dondervogel 2 (talk) 18:37, 22 October 2017 (UTC)

I think the information about unit symbols defined in an IEEE standard is useful reference material, and that in discussing a unit, its symbol(s) (especially those in law, in standards and common use) could be given. What Wikipedia seems to lack is a way of suitably organizing reference information for incorporating into articles; here, for example, is information organized in a way that would be a useful resource for editing several articles, but without an obvious place to put it. Perhaps this discussion would be most useful if its focus recognized the potential value of this information, and sought to propose ways to make it usefully available? Given Wikipedia's structure of main articles and associated talk pages, an "article for editors" somehow seemed to be natural. I, for one, have sorely felt the lack of just such a list of units when editing articles on units of measurement. —Quondum 21:58, 22 October 2017 (UTC)

This sounds like a suggestion for a Wikisource of documents that do not meet Wikisource's legal requirement for works to be licensed or free of copyright, but from which all useful information is extracted. That's an idea for the Idea Lab at the Village Pump, but I can see it facing numerous problems. There's the ethical and legal question of how far we should go in such a process, the hazards of editors relying on another editor's abstract rather than the source but presenting and citing material as if it came from the source, the risk that a source will be given undue primacy and authority merely because it's been wikisourced, the question of which documents should be worthy of inclusion, the expansion of Wikipedia's maintenance problems into ensuring the wikisourced material employs the latest editions and an overall problem of mission creep, and I'm sure the strategic thinkers at the pump will come with more - but they might also come up with constructive suggestions! 92.19.24.9 (talk) 12:14, 23 October 2017 (UTC)

I do not intend to get involved in exploring options for a general mechanism. In the interim, we have made do. And until this information has been comprehensively merged into the respective articles with citation, I think it is the most efficient means of collecting this particular information in usable form. And, aside from general style arguments, I don't see a solid argument for avoiding putting this into main space, until Wikipedia editors actually start generally adhering to such high-level guidelines. Personally, I don't care whether this goes into main space as a table, only that the unit symbols be available. —Quondum 02:38, 24 October 2017 (UTC)

Name

The Wikipedia convention for naming articles on IEEE standards is simply "IEEE nnnn" and "IEEE nnn-nn", without "Std". We use "IEEE nnn-yyyy" occasionally for superseded standards (e.g. IEEE 754-1985 but IEEE 754 for the current standard). Similarly, we do not put "Std" after ISO, ASME, BS, SAE, DIN, JIS and others. 92.19.24.9 (talk) 12:59, 22 October 2017 (UTC)

The standard refers to itself as "IEEE Std 260.1-2004", and the complete citation provided is "IEEE Std 260.1™-2004 (Revision of IEEE Std 260.1-1993)". By comparison, ISO standards are all of the form ISO nnnnn:yyyy (not ISO nnnnn-yyyy) and are referred to as such. What name do you suggest for the present article? Dondervogel 2 (talk) 13:12, 22 October 2017 (UTC)

You're describing the full names of standards and how we refer to standards when we use them as sources. But we don't name our articles about standards in those ways. See ISO 9000, IEEE 754, ASME B5, DIN 1451, SAE J1772 and so on. This article should be named IEEE 260.1. 92.19.24.9 (talk) 13:26, 22 October 2017 (UTC)

If other editors agree, please go ahead and rename the article. I do not object. Dondervogel 2 (talk) 13:40, 22 October 2017 (UTC)

Given the discussion in #Why? above, I think that it is not yet clear what how this standard should be presented. Is it notable? (Notice that notability is about the topic, not the content of the article.) A suitable title is also not that obvious, despite "Wikipedia convention". Maybe IEEE 260 should discuss all its contained parts and their versions in a single place? —Quondum 22:12, 22 October 2017 (UTC)

How about this then for a way ahead:

# We rename this article 'IEEE 260', broadening its scope to all sub-parts.

# We create a new article entitled 'List of units outside the SI, including standard symbols and definitions'

Dondervogel 2 (talk) 07:08, 23 October 2017 (UTC)

Are you prepared for such a very wide scope and are you aware it duplicates other articles? "Units outside the SI" encompasses units already well presented in United States customary units, Imperial units, Indian units of measurement, Myanmar units of measurement, Lorentz–Heaviside units, Gaussian units, Natural units and more, such as the articles listed in System of measurement, collected in the template Template:Systems of measurement or categorised in Category:Systems of units. This task is already largely accomplished by the extensive tables of names, symbols, definitions and relations to SI in Conversion of units which seeks to include everything you've tabulated above, other non-SI units and the SI units too, and does a fairly good job of it, though it doesn't wander into the minefield of abbreviations listed at Kilometres per hour. I admit I wasn't aware of Conversion of units when I suggested a "List of..." approach. Obviously I must withdraw that suggestion. You could review Conversion of units with IEEE 260.1 at hand, focusing particularly on omissions but not replacing precise values with approximations. However, it would be a mistake to describe any symbols as "the IEEE symbol" as Dondervogel 2 has done at Cubic foot and Cubic yard. IEEE 260.1 is just one example of the many standards and documents that describe the formal symbols for units of measurement. It constitutes a useful reference for citations, but to describe a symbol as "the IEEE symbol" is too restrictive - suggesting acceptance of the symbol is restricted to those who follow IEEE standards - and also wrongly suggests that IEEE has the same authority over letter symbols outside SI as CGPM has over SI. 92.19.24.9 (talk) 10:29, 23 October 2017 (UTC)

While in principle, broadening/changing the scope to cover the standard might be in line with other articles on standards, this is not my focus. And now that I am aware of Conversion of units, which explicitly lists symbols of units, I think that merging this into that in the form of citations for individual symbols might be appropriate. The value would be this: when editing Yard, for example, (which seems to imply that it has no symbol, only an abbreviation), Conversion of units presently provides no citation for the symbol and cannot be used as a source. With a citation in Conversion of units, as an arbitrary editor I could edit Yard to give the symbol yd, citing IEEE 260.1-2004. Which was (my part of) the original purpose for this article. —Quondum 11:55, 23 October 2017 (UTC)

It's true that if there were a citation in Conversion of units, another editor who was aware of Conversion of units could more easily find a citation for Yard. But the principle of personal editorial responsibility still applies. As WP:SAYWHEREYOUREADIT puts it, you should cite "sources directly only if you have read the source yourself". Coupled with the principle of WP:V that Wikipedia is not a reliable source and we do not cite it, together with the hypertext foundation of Wikipedia, this does add a further obstacle to repeating the same extensive information in multiple articles. Nevertheless the temptation is bound to remain, and so we have the same information in Conversion of units as in articles such as United States customary units and in individual articles. Of the three article types, Conversion of units may be the least likely to be found by readers and the least likely to be reviewed by editors, and while anyone visiting Conversion of units and seeking verification of one point can easily click into the specific article, movement in the opposite direction would be surprising. All in all, Wikipedia's structure means that ensuring articles such as Yard are fully referenced has more value than adding to Conversion of units. 92.19.24.9 (talk) 13:25, 23 October 2017 (UTC)

Related standards

From The International System of Units (SI) – 8th edition 2006 §1.2:

Many of the quantities, their recommended names and symbols, and the equations relating them, are listed in the International Standards ISO 31 and IEC 60027 produced by Technical Committee 12 of the International Organization for Standardization, ISO/TC 12, and by Technical Committee 25 of the International Electrotechnical Commission, IEC/TC 25. The ISO 31 and IEC 60027 Standards are at present being revised by the two standardization organizations in collaboration. The revised harmonized standard will be known as ISO/IEC 80000, Quantities and Units, in which it is proposed that the quantities and equations used with the SI will be known as the International System of Quantities.

An early draft of the proposed 9th edition] essentially says the same thing in the past tense:

Many of the quantities, with their corresponding names and symbols, and the equations relating them, were listed in the international standards ISO 31 and IEC 60027 produced by Technical Committee 12 of the International Organization for Standardization, ISO/TC 12, and by Technical Committee 25 of the International Electrotechnical Commission, IEC/TC 25. These standards have been revised by the two organizations in collaboration, and are known as the ISO/IEC 80000 Standards, Quantities and Units, in which the corresponding quantities and equations are described as the International System of Quantities.

This suggests a section that lists related standards and puts this one into context. It also suggests that we'd find that ISO/IEC 80000 effectively supersedes IEEE 260.1, which would be worth ascertaining. And indeed, ISO 80000 looks so similar in its presentation of units that it may have used the same source as IEEE 260.1 or perhaps even IEEE 260.1 itself. —Quondum 13:06, 28 October 2017 (UTC)

ISO/IEC 80000 cannot supersede IEEE 260.1 because it's scope is different. One important difference is that the customary inch-pound units are deprecated by ISO/IEC 80000. IEEE 260.1 is the only standard I know of to define symbols for units like lb, ft, etc - hence its unique value Dondervogel 2 (talk) 13:35, 28 October 2017 (UTC)

In the new versions, perhaps, but in ISO/IEC 80000-3:2007 they list in an annex these units and symbols: gal (Gal), inch (in) with a mention of mil and thou, foot (ft), yard (yd), mile (mi) (statute and US Survey), square inch (in²), square foot (ft²), square yard (yd²), square mile, acre, cubic inch (in³), cubic foot (ft³), cubic yard (yd³), gallon (UK) (gal (UK)), pint (UK) (pt (UK)), fluid ounce (UK) (fl oz (UK)), bushel (UK), gallon (US) (gal (US)), ..., light year (abbrev: l.y.), astronomical unit (ua), parsec (pc), year (a). I've skipped some volume, speed and acceleration units. Perhaps lb etc. would be covered in ISO/IEC 80000-4:2007? —Quondum 15:23, 28 October 2017 (UTC)

And yes, even the 2007 versions says "The use of these units is deprecated", but it nevertheless gives symbols. —Quondum 15:48, 28 October 2017 (UTC)

I see what you mean. I had focused my attention on the "deprecated" and not noticed that symbols (and definitions) are nevertheless provided for many units. As pointed out by anon, they could usefuly be used to correct some of the misleading symbols listed in Conversions of units. I see that both standards use 'ua' as the symbol for astronomical unit, for example. Dondervogel 2 (talk) 17:02, 28 October 2017 (UTC)

For what it's worth, I expect a revision of ISO 80000-3 to be published in 2018 or 2019. I do not expect the revision to define or provide symbols for any of the deprecated units, leaving us with only the IEEE standard. Dondervogel 2 (talk) 19:09, 28 October 2017 (UTC)

I don't follow your logic. A newer revision superseding an older revision does not stop that older revision being a reference for what it provided. Also, IEEE 260.1 is presumably already effectively superseded by ISO 80000 (in the view of IEEE). —Quondum 21:37, 28 October 2017 (UTC)

The revision of a standard implies the withdrawal of all previous editions of that standard; withdrawal would not prevent the old version being cited, it just means that ISO no longer recognizes the withdrawn symbols and definitions. IEEE 260.1-2014 (reaffirmed in 2010) is listed here as an active standard. IEEE sometimes withdraws standards but has chosen not to withdraw this one, so it is still current. Dondervogel 2 (talk) 22:01, 28 October 2017 (UTC)

Okay, so IEEE has not deferred authority/successorship to ISO/IEC on this standard, though it references ISO 31, and by implication its successor, ISO 80000. However, we evidently do have an as-yet current parallel standard that list many or most of the symbols for US customary units, and so IEEE 260.1 is not really unique in any sense. In general, I'd say that it makes sense to cite both standards for symbols where they mention them. —Quondum 00:34, 29 October 2017 (UTC)

Yes, until such time as ISO 80000-3:2006 is superseded, I agree. To be honest I'm more interested in examples where IEEE and ISO standards clash - I can think of just one such example (b vs bit). Dondervogel 2 (talk) 10:48, 29 October 2017 (UTC)

Are you forgetting b vs Sh? I prefer the symbol bit to b, in part because the latter clashes with b for barn, which is already defined by SI. And I definitely prefer the shannon to the bit as a unit of information, principally because so many people fail to realize that they measure different things, as with lb and lbf. —Quondum 21:24, 29 October 2017 (UTC)

Not forgetting - I just wasn't thinking along those lines, so it had not occurred to me. Is your point that IEEE allows the bit to be defined in two different ways, one corresponding to the ISO bit and the other to the shannon? Dondervogel 2 (talk) 22:14, 29 October 2017 (UTC)

I also prefer the symbol 'bit' btw, but mainly to avoid confusion with 'B' for byte, often written in lower case, which reminds me of the ambiguity between the symbols for bel and byte, not addressed by either standards organization. I wonder if one day they will be distinguished by Be and By or similar. That certainly won't happen overnight! Dondervogel 2 (talk) 22:19, 29 October 2017 (UTC)

Information and storage capacity are different quantities, and giving them differently named units will prevent a lot of confusion. But we're probably saying the same thing. I disagree with the byte, an ill-defined customary unit, being defined at all in a standard. It is like ISO defining the ell as being half a smoot, except on Wednesdays. ISO is guilty of some fuzzy thinking IMO, with associated logical fallacies built into the system: 1/(ln 2) = 1 = 2π. The ISQ and SI could be made far more usable. —Quondum 01:01, 30 October 2017 (UTC)

I agree there are logical fallacies but my criticisms differ from yours (Parts 1 and 3 of ISO 80000 are incompatible with one another). My main concern is the definition of 'level of a field quantity', which I consider unnecessary and can best be deleted. We shall see. Dondervogel 2 (talk) 10:57, 30 October 2017 (UTC)

I don't follow your exact concern: I see no inconsistency between Part 1 and Part 3. I think the whole history of levels is unfortunate, though, with ratios of field quantities being assigned the same dB levels as for the associated power levels. It gets even murkier when you realize that pressure is both a field quantity (accoustic field) and a power quantity (electromagnetic field). Back to your point: nepers were evidently defined in terms of ratios, especially of field quantities, but it seems (to me, at least) that someone messed up in re-interpreting neper levels in light of the field/power model in use with the bel, which is ill-defined from the perspective of a general system of measurement. —Quondum 04:17, 31 October 2017 (UTC)

The inconsistency I was referring to is the use by Part 3 of the term "field quantity", deprecated by Part 1. Dondervogel 2 (talk) 07:45, 31 October 2017 (UTC)

I see what you are referring to. However, it seems clear to me that the term "field quantity" used Part 3 (dated 2007) has since been deprecated in Part 1 (dated 2009) with the term "root-power quantity" being provided as a replacement. As such, all that is likely to happen is a substitution of the term in the next version of Part 3, with no other effective change. I would not expect a deletion of any definition. It would be difficult to retain the definition of the neper as it is without defining the distinction. —Quondum 11:51, 31 October 2017 (UTC)