Molecular Weight Calculator

Find the molecular weight of a chemical formula from its atoms, using IUPAC standard atomic weights.

Chemical formula	C6H12O6

Chemical formula

Case matters: Co is cobalt, CO is carbon monoxide. Use ( ) and · for hydrates, e.g. CuSO4·5H2O.

Molar mass

180.156 g/mol

C6H12O6: C6 H12 O6.

Mass composition

C40%: 40%
H7%: 6.7%
O53%: 53.3%

By element

Element	Atoms	Atomic weight	Mass	Mass %
C	6	12.011	72.066	40%
H	12	1.008	12.096	6.71%
O	6	15.999	95.994	53.28%

About the Molecular Weight Calculator

Type a chemical formula to get its molecular weight. Case matters (Co is cobalt, CO carbon monoxide); brackets and hydrates such as CuSO4·5H2O work too.

Molar mass is the sum of the atomic weights of every atom in the formula, in grams per mole. Atomic weights here are the IUPAC Commission on Isotopic Abundances and Atomic Weights' abridged standard values. Molecular weight (in daltons) has the same number.

The formula

M = Σ (atoms of element × standard atomic weight)

Worked example

Glucose, C6H12O6

6 carbon + 12 hydrogen + 6 oxygen atoms
= 180.156 (g/mol, or daltons per molecule)

Questions people ask

Molar mass or molecular weight?

Numerically the same: g/mol vs daltons (u).

Why are some values rounded?

Isotope ratios vary in nature, so IUPAC gives abridged values to the precision that's meaningful.

Sources

CIAAW: Abridged standard atomic weights