Molar Mass Calculator
Calculate the molar mass of any chemical formula in g/mol, including parentheses and hydrates, with the mass percentage of each element.
M = Σ ni · Ar,i
How to use this calculator
- Type your input in the box.
- The result updates as you type.
- Use “Copy result” or “Copy link” to share it.
The molar mass M of a compound is the mass of one mole of it, in grams per mole. It equals the sum of the atomic weights of all atoms in the formula, each multiplied by how many times it appears.
Type a formula such as Ca(OH)2, K4[Fe(CN)6] or the hydrate CuSO4·5H2O. The calculator uses IUPAC standard atomic weights and also gives the percent composition by mass, which you need for empirical-formula problems.
Worked example
Glucose, C6H12O6: 6 × 12.011 + 12 × 1.008 + 6 × 15.999 = 180.156 g/mol. Carbon makes up 40.00 % of its mass.
Frequently asked questions
Is molar mass the same as molecular weight?
Numerically yes. Molecular weight (relative molecular mass) is dimensionless, while molar mass has units of g/mol. For water both are about 18.015.
How do I enter a hydrate?
Use a middle dot, an asterisk or a period between the parts, with the water coefficient in front: CuSO4·5H2O, CuSO4*5H2O or CuSO4.5H2O.