It is possible to calculate the approximate molecular weight of a macromolecule using SEC
Determine the column void volume, Vo (volume a particle sees if it cannot penetrate any pores) by flowing dextran blue (a huge molecule, m.w. 2 MDa) through the column
Determine elution volumes Ve of several macromolecules of known molecular weight
Plot a calibration curve: log(m.w.) vs. Ve/Vo
Measure Ve of the analyte (a macromolecule of unknown m.w.), read off m.w. from calibration curve