The Molecular Weight Calculator finds the molar mass of a chemical compound from its formula and shows each element's contribution.
Molar mass of H2O = 18.0150 g/mol
| Molecular weight | 18.0150 g/mol |
| H × 2 | 2.0160 g/mol (11.19%) |
| O × 1 | 15.9990 g/mol (88.81%) |
Molecular weight (molar mass) is the sum of the atomic weights of all atoms in a molecule, in grams per mole. Water, H₂O, is 2 × 1.008 + 15.999 = 18.015 g/mol.
Use element symbols with correct capitalisation (Co is cobalt, CO is carbon monoxide), numbers for counts and parentheses for groups: C6H12O6 (glucose), Ca(OH)2, Al2(SO4)3.
Molar mass converts between grams and moles, which chemists need to prepare solutions (see the Molarity Calculator), balance reactions and calculate yields.
CO₂ 44.01; NaCl 58.44; NH₃ 17.03; H₂SO₄ 98.08; C₆H₁₂O₆ 180.16; CaCO₃ 100.09 g/mol.
What is a mole? 6.022 × 10²³ particles.
Why are atomic weights not whole numbers? They average natural isotopes.
Can I enter hydrates like CuSO4·5H2O? Write it as CuSO4(H2O)5.