Molar Mass Calculator – Formula & Examples

Element	Name	Atoms	Atomic mass	Mass (g/mol)	Percent
O	Oxygen	6	15.999	95.994	53.284%
C	Carbon	6	12.011	72.066	40.002%
H	Hydrogen	12	1.008	12.096	6.714%

Element

Name

Atoms

Atomic mass

Mass (g/mol)

Percent

Oxygen

15.999

95.994

53.284%

Carbon

12.011

72.066

40.002%

Hydrogen

1.008

12.096

6.714%

About the Molar Mass Calculator

Molar mass is the mass of one mole of a substance in grams. Add up the atomic mass of every atom in the formula and you have it. This calculator parses brackets, hydrates and nested groups — type something like Ca(OH)2 or CuSO4·5H2O and it gives the molar mass plus the mass contributed by each element.

Also known as: molecular weight calculator, molar mass of a compound, formula mass, molecular mass, gram formula mass, mw calculator.

How to use this calculator

Type the formula exactly as written — capital letters start an element, lowercase continue it.
Use brackets for groups, e.g. Al2(SO4)3.
Use a dot for hydrates, e.g. CuSO4·5H2O or CuSO4.5H2O.

Formula

M = Σ (atoms of each element × atomic mass)

Worked example

Using the values pre-filled in the calculator above:

Chemical formula: C6H12O6
Sample mass (optional) = 0 g

the calculator returns:

Molar mass: 180.156 g/mol
Atoms per molecule: 24
Different elements: 3

Working

O: 6 × 15.999 = 95.9940 g/mol
C: 6 × 12.011 = 72.0660 g/mol
H: 12 × 1.008 = 12.0960 g/mol

Frequently asked questions

What is the difference between molar mass and molecular weight?

Numerically they are the same. Molecular weight is a relative, unitless number; molar mass carries the units g/mol.

How do I type a hydrate?

Use a dot or a full stop before the water part: CuSO4·5H2O or CuSO4.5H2O both work.

Why does my textbook give a slightly different value?

Atomic masses are periodically revised and some books round differently. Differences are normally in the third decimal place.

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