⚖️ 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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