g/mol

gram per mole

Molar massexact by definition

The gram per mole is the working unit of molar mass, and it is arranged so that a substance's molar mass in g/mol is numerically the same as its relative molecular mass read off the periodic table. Water is 18.015 g/mol, sodium chloride 58.44, calcium carbonate 100.09. The conversion to kg/mol is exactly 0.001, a decimal prefix.

Watch out: Since the 2019 redefinition of the mole, the equality between atomic mass units and grams per mole is no longer exact by definition. The molar mass constant is now a measured 0.99999999965 g/mol, with an uncertainty in the tenth decimal place. This changes nothing in practice and matters only in metrology.

1 g/mol 1 g/mol