Molar mass calculator
Type a chemical formula, like H2SO4, Ca(OH)2 or CuSO4·5H2O, and see the molar mass in g/mol, the percent composition of each element and the mass of any number of moles.
How to useMolar mass and percent composition
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Molar mass calculator: what it is for
Type the formula of any substance, like H2SO4, C6H12O6 or CuSO4·5H2O, and the tool adds up the atomic masses of each element to give the molar mass in g/mol. The table shows how many atoms of each element are in the formula, the mass each contributes and the percent composition by mass. Enter an amount in moles to get the mass in grams.
Calculations run in your browser, using IUPAC standard atomic masses.
How to use
- Type the chemical formula with correct upper and lower case.
- See the molar mass and composition.
- Enter moles to convert to grams.
When to use it
- Solving stoichiometry problems.
- Preparing solutions in the lab.
- Checking a compound's empirical formula.
Frequently asked questions
How is molar mass calculated?
Add up each element's atomic mass multiplied by the number of its atoms in the formula. For water (H2O): 2 × 1.008 + 15.999 = 18.015 g/mol.
Does the tool accept parentheses and hydrates?
Yes. Use parentheses or brackets for groups, like Ca(OH)2 and K4[Fe(CN)6], and a dot or · for hydrates, like CuSO4·5H2O. Mind upper and lower case: Co is cobalt and CO is carbon monoxide.
Where do the atomic masses come from?
They're IUPAC standard atomic weights, rounded. For radioactive elements with no stable isotope, the mass number of the most stable isotope is used.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.