Molar Mass Calculator

Molar mass converts between the microscopic world of atoms and the macroscopic world of grams on a balance. One mole contains Avogadro's number of entities (6.022 × 10²³) and weighs the molar mass in grams. Every stoichiometry problem, solution preparation, and percent composition calculation starts here — without correct g/mol, mole ratios mislead and yields fail in the lab.

Molar mass from formula:

M = Σ (n_i × A_i)

Where M is molar mass in g/mol, n_i is the count of each element, and A_i is atomic mass from the periodic table. For compounds: sum all atoms. For ions, include net charge only if calculating formula unit mass of salts. Hydrates list waters explicitly: CuSO₄·5H₂O includes five water molecules in the sum.

Enter a formula like H₂SO₄, Ca(OH)₂, or C₆H₁₂O₆. Parentheses multiply subscripts. The calculator parses element symbols and counts, then multiplies by standard atomic weights (IUPAC values). Water H₂O: 2(1.008) + 15.999 = 18.015 g/mol. Sulfuric acid H₂SO₄: 2(1.008) + 32.06 + 4(15.999) = 98.079 g/mol.

Worked example: How many grams of NaCl for 0.50 mol? M(NaCl) = 22.99 + 35.45 = 58.44 g/mol. Mass = 0.50 × 58.44 = 29.22 g. Glucose C₆H₁₂O₆: 6(12.011) + 12(1.008) + 6(15.999) = 180.156 g/mol. A 90.1 g sample is 90.1/180.156 = 0.500 mol.

Feed molar mass into the molarity and dilution calculators for solution prep, and the ideal gas law when converting between grams and moles of gases. Percent composition and empirical formula problems all depend on accurate M.