⚖️ Molar Mass Calculator
Enter a chemical formula, even hydrates like CuSO₄·5H₂O or nested groups like Fe₂(SO₄)₃, and get its exact molar mass with a per-element breakdown.
Molar mass
180.156 g/mol
| Element | Atoms | Atomic wt | Mass | Mass % |
|---|---|---|---|---|
| O Oxygen | 6 | 15.999 | 95.994 | 53.28% |
| C Carbon | 6 | 12.011 | 72.066 | 40.00% |
| H Hydrogen | 12 | 1.008 | 12.096 | 6.71% |
| Total | 180.156 | 100% | ||
IUPAC/CIAAW standard atomic weights. Parser handles nested groups, hydrates (· / . / *) and two-letter symbols. 🔒 Computed in your browser.
How the molar mass calculator works
The formula is parsed with a recursive-descent parser that handles nested parentheses and brackets, hydrate dots (CuSO₄·5H₂O), and greedy two-letter element symbols (so “Co” is cobalt, not carbon + oxygen). Each element’s count is multiplied by its standard atomic weight and summed to give the molar mass in g/mol; the per-element mass ÷ total gives percent composition.
Atomic weights are the IUPAC/CIAAW standard values. The parser is what a chatbot gets wrong. It fumbles hydrates and the Co-vs-C+o ambiguity, so this gives the exact mass with the working shown, every time.
Frequently asked questions
How do I calculate molar mass?
Add up the atomic weight of every atom in the formula. For H₂O: 2 × 1.008 (H) + 1 × 15.999 (O) = 18.015 g/mol. This tool parses the formula and does the summation exactly, showing each element’s contribution.
Does it handle hydrates like CuSO₄·5H₂O?
Yes. Write the dot as ·, . or *; the five waters are added to the formula, giving 249.68 g/mol for copper(II) sulfate pentahydrate. Many calculators and chatbots get hydrates wrong.
What about nested groups like Fe₂(SO₄)₃?
The parser expands nested parentheses and brackets correctly, Fe₂(SO₄)₃ is 2 Fe, 3 S, 12 O = 399.88 g/mol, and K₄[Fe(CN)₆] is handled too.
What is the difference between molar mass and molecular weight?
Numerically they are the same value; molar mass carries units of g/mol (mass of one mole) while molecular weight is the dimensionless relative mass. This tool reports g/mol.
Which atomic weights are used?
The IUPAC/CIAAW standard atomic weights (conventional abridged values). These change only rarely, on the order of once every two decades per element, so results are stable.
Is my input uploaded?
No, parsing and the calculation run entirely in your browser.
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