This molar mass calculator adds up atomic weights from the periodic table for any formula you enter, including hydrates and parentheses.
Chemistry
Molar Mass Calculator
Parse formulas and calculate molar mass of compounds.
Calculator
About this calculator
Formula notes
M = Σ(count of each element × its atomic weight). Parentheses multiply everything inside; hydrates add after the dot.
Worked examples
- Example: H2O = 2×1.008 + 15.999 = 18.015 g/mol.
- Ca(OH)2 contains 1 Ca, 2 O, and 2 H atoms; standard atomic weights give a molar mass of about 74.09 g/mol.
How to use it
- Type the chemical formula, like H2O or Ca(OH)2.
- Check the per-element breakdown if shown.
- Read the total molar mass in g/mol.
Frequently asked questions
Why is water 18.015 and not exactly 18?
Atomic weights are weighted isotope averages, so H is 1.008 rather than 1.
How are parentheses handled?
The subscript after a parenthesis multiplies every element inside it.
Limits and interpretation
- Atomic-weight values can vary slightly by reference and isotopic composition, so the final decimals are not universal constants.
- The formula parser does not determine sample purity, hydration state, or whether the written compound is chemically plausible.