Molar Mass

Definition

The mass of one mole of a substance, in grams per mole. Add up the atomic weights of every atom in the formula to find it.

$M = \frac{m}{n}$

Unit: g/mol

Technical definition

Molar mass is the mass of one mole of a substance, numerically equal to the sum of the standard atomic weights of its constituent atoms, expressed in g/mol. It converts directly between a sample's mass and its amount in moles.

Example

Water (H2O) has a molar mass of about 18.015 g/mol: 2(1.008) + 15.999 = 18.015.

Common confusion

Molar mass is not molecular mass. Molar mass is per mole (g/mol), while molecular mass describes a single molecule in atomic mass units.