Molecular Weight Calculator
Type a chemical formula using capital letters for elements.
This result is an estimate only. Double-check important figures before relying on them.
How it is calculated
- Each element’s atomic mass × the number of atoms, added together
- Brackets multiply the group inside them
- A dot (·) joins hydrate water, multiplied by its leading number
For the percentage of each element, use the percent composition calculator.
Worked example
Glucose, C6H12O6:
- 6 × 12.011 + 12 × 1.008 + 6 × 15.999 = 180.156 g/mol
- 24 atoms
Why your number may differ
This covers elements 1 to 92. Charges, isotopes and polymers are not handled.
Frequently asked questions
How is molecular weight calculated?
Add the atomic mass of every atom in the formula, using brackets and numbers as multipliers.
Does it handle hydrates?
Yes. Write the water of crystallisation after a dot, as in CuSO4.5H2O.
Why do different tables give slightly different values?
Atomic masses are averages that are revised from time to time. This tool uses standard conventional values to three decimals.