Molar mass calculator for a chemical formula
Type a chemical formula (H2O, Ca(OH)2, CuSO4·5H2O…): you get its molar mass and the mass share of each element.
Result
249.677 g/molMolar mass
- Cu × 1: 63.546 g/mol, that is 25.45 %
- S × 1: 32.06 g/mol, that is 12.84 %
- O × 9: 143.991 g/mol, that is 57.67 %
- H × 10: 10.08 g/mol, that is 4.04 %
Inputs
- Chemical formula
- CuSO4·5H2O
How it is calculated
The formula is read element by element, multiplied by subscripts and by groups in brackets.
Result
Molar mass
How it is calculated
- The formula is read element by element, multiplied by subscripts and by groups in brackets.
- A hydrate “·5H2O” adds H2O five times.
- Molar mass = sum of (number of atoms × atomic weight). Share of an element = its mass ÷ molar mass.
- Atomic weights: IUPAC abridged table (CIAAW 2021, zirconium revised in 2024).
Example
CuSO4·5H2O: Cu 63.546 + S 32.06 + 9 O (143.991) + 10 H (10.08) = 249.677 g/mol. Copper makes up 25.45 % of the mass.
Good to know
- Atomic weights are natural average values; an isotope-enriched sample can differ.
- Charges (ions) and compound names are not read: type the formula.
- Formula limited to 100 characters.
Sources
- IUPAC CIAAW, Standard atomic weights (abridged, 2021; 2024 zirconium revision)
Frequently asked questions
What is this tool used for?
Type a chemical formula (H2O, Ca(OH)2, CuSO4·5H2O…): you get its molar mass and the mass share of each element.
How is the result calculated?
The formula is read element by element, multiplied by subscripts and by groups in brackets.
What should I check before using the result?
Atomic weights are natural average values; an isotope-enriched sample can differ.