Molar Mass Calculator
Enter the number of atoms of each element in your compound to instantly calculate the molar mass (molecular weight) in grams per mole.
How to use this molar mass calculator
- Enter the number of atoms of each element in your compound.
- Leave elements not in your compound at 0.
- Example — water (H₂O): H=2, O=1 → 18.015 g/mol.
- Example — glucose (C₆H₁₂O₆): C=6, H=12, O=6 → 180.156 g/mol.
Formula
M = Σ(nᵢ × Aᵢ). Atomic masses: H=1.008, C=12.011, N=14.007, O=15.999, Na=22.990, Cl=35.453, S=32.065, Ca=40.078 g/mol.
About the Molar Mass Calculator
Molar mass is one of the most fundamental quantities in chemistry — you need it to convert between grams and moles, calculate concentrations, and determine percent composition.
Water (H₂O) = 18.015 g/mol means one mole of water weighs 18.015 g. A 500 mL bottle of water contains roughly 27.7 moles of H₂O molecules.
Frequently asked questions
+What is molar mass?
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, expressed in g/mol. It equals the sum of atomic masses of all atoms in a formula unit.
+Is molar mass the same as molecular weight?
In everyday chemistry they are used interchangeably. Technically molar mass is in g/mol while molecular weight is a dimensionless ratio (in amu), but numerically equal.
+What about elements not listed?
For other elements, look up the atomic mass on a periodic table, multiply by atom count, and add to this result manually.