Molecular Weight Calculator
Type a chemical formula and get its molar mass in g/mol, with a per-element breakdown and mass percentages. Handles parentheses and hydrates like CuSO4.5H2O.
Chemical formula
How to use this calculator
1. Type the formula exactly
Element symbols are case-sensitive: Co is cobalt, while CO is carbon plus oxygen. Numbers follow the symbol they multiply, as in H2O.
2. Use parentheses for groups
Wrap repeating groups in parentheses with a multiplier, like Ca(OH)2 or Al2(SO4)3. Parentheses can be nested.
3. Add hydrates with a dot
Crystal water is written after a dot, for example CuSO4.5H2O or CuSO4·5H2O. The number before the hydrate multiplies that whole fragment.
4. Read the breakdown
The big number is the molar mass. The table lists each element's atom count, mass contribution, and percentage of the total — handy for the molarity calculator.
About molecular weight
Molar mass
Molar mass is the mass of one mole of a substance, equal to the sum of the standard atomic weights of all its atoms, in grams per mole (g/mol).
Atomic weights used
This tool uses standard atomic weights from the periodic table for a broad set of common elements. Values are rounded conventional figures, accurate enough for typical lab and homework work.
Unknown symbols
If you enter a symbol the calculator does not recognise — a typo or an exotic element — it shows a friendly error naming the symbol so you can fix it instead of getting a wrong number.