Molar MassHow the converter works
It first finds the molar mass of your formula from the IUPAC atomic weights. Then it uses two simple relations. Moles equal grams divided by molar mass. The number of particles equals moles multiplied by the Avogadro constant, 6.02214076 × 1023. For a substance made of molecules, the particles are molecules. For a salt they are formula units, and for a metal or a noble gas they are atoms.
The solution maker
Molarity is moles of dissolved substance per litre of solution. The mass to weigh is molarity × volume in litres × molar mass. Dissolve that mass in less water than the final volume, then add water up to the mark of a volumetric flask. If your bottle holds a hydrate, type the hydrate formula, for example CuSO4.5H2O, because the water in the crystals is part of what you weigh.
Good to know
- Mass must be in grams. 1 kg is 1000 g and 1 mg is 0.001 g.
- For oxygen, nitrogen, hydrogen and chlorine gas, type O2, N2, H2 and Cl2.
- Nothing you type leaves your browser.
The method, with worked examples, is on the pages grams to moles, the mole and the Avogadro constant and molarity and solutions.
Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.