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Molar Mass Calculator
Calculate molar mass, atom counts, element contributions, and mass percentages from formulas with groups and hydrates entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Chemical formula
Element symbols are case-sensitive. Parentheses, brackets, and hydrate dots are supported.
Try an example
Formula guide
- NaCl
- Element symbols
- H2O
- Numeric subscripts
- Ca(OH)2
- Grouped atoms
- CuSO4·5H2O
- Hydrates / adducts
Molar mass
18.015
g/molH2O
| Element | Atoms | Mass | Share |
|---|
Mass composition
by elementAtomic weights are conventional standard values rounded for practical calculations. Results may differ slightly from isotope-specific or interval-based references.
How it works
- Enter a chemical formula using correctly capitalized element symbols.
- The calculator expands groups and counts every atom in the compound.
- Review total molar mass, element contributions, and mass percentages.
FAQ
How is molar mass calculated?
The calculator counts each element in the formula, multiplies that count by its conventional atomic weight, and adds every contribution to give grams per mole.
Can I use parentheses and hydrates?
Yes. Nested parentheses or brackets, numeric subscripts, leading coefficients, and hydrate separators such as the middle dot in CuSO4·5H2O are supported.
Why might another reference show a slightly different value?
Published atomic weights can be presented as intervals or rounded to different precision. This calculator uses practical conventional values, while isotope-specific compounds require isotope masses.
Does the formula leave my browser?
No. The formula parser, element lookup, and composition calculations run locally with a built-in periodic-table dataset.
Reading the result
Molar mass
The mass of one mole of the compound, expressed in grams per mole.
Atom count
The number of atoms of each element after groups and coefficients expand.
Mass share
Each element’s percentage contribution to the compound’s total mass.