What is molar mass?
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). One mole contains Avogadro's number of particles—approximately 6.022 × 10²³ atoms, molecules, or ions. The molar mass of a compound equals the sum of the atomic masses of every atom in its formula. For water (H₂O), that is 2 × 1.008 + 15.999 = 18.015 g/mol. Molar mass is the bridge between the microscopic world of atoms and the macroscopic world of grams that you can weigh on a balance.
How to use this calculator
Type a chemical formula into the input field—capitalise the first letter of each element symbol and add subscript numbers (e.g. H2O, NaCl, C6H12O6). Quick-pick buttons for seven common compounds save typing. Click Calculate to see the molar mass, an element-by-element breakdown with atomic masses and subtotals, and a coloured percent-composition bar. Optionally enter a mass in grams in the second field to see the corresponding number of moles and molecules instantly.
Grams-to-moles conversion
Once you know the molar mass, converting between grams and moles is straightforward: moles = mass (g) / molar mass (g/mol). This calculator does it for you—just type the mass in the optional field and the result card shows both the moles and the exact number of molecules. This is especially useful when preparing solutions of a specific molarity or performing stoichiometric calculations.
Practical applications
Chemists use molar mass daily to weigh out reagents for reactions, prepare standard solutions, and calculate theoretical yields. Pharmacologists rely on it to convert drug doses between mass and molar units. Biochemists determine protein sizes from amino-acid sequences. Environmental scientists express pollutant concentrations in both mg/L and µmol/L, requiring molar mass for the conversion. In every discipline that touches chemistry, molar mass is indispensable.
Tips
Element symbols are case-sensitive—"Co" is cobalt, "CO" is carbon + oxygen. This calculator supports simple formulas without parentheses; for hydrates or complex salts, expand them first. Atomic masses follow IUPAC standard values. This free tool runs entirely in your browser—no sign-up, no download, and instant results on any device. Bookmark it for quick molar-mass lookups whenever you need them.