Convert between grams, moles and particle counts using molar mass and Avogadro's number.
Molar mass is the mass of one mole of the substance — for water it is 18.015 g/mol. A separate chemistry tool covers working out molar mass from a formula.
moles
How to use this tool
Pick “Moles from mass” if you weighed a sample, or “Mass from moles” if you know how many moles a reaction needs.
Type the mass in grams or the amount in moles, depending on the direction you chose.
Type the substance's molar mass in g/mol — water is 18.015, table salt (NaCl) is 58.44, glucose is 180.156.
The headline is the answer in the direction you asked, with the particle count from Avogadro's number alongside.
Formula & worked example
36.03 g of water (molar mass 18.015 g/mol) is 36.03 ÷ 18.015 = 2.000 mol, containing 2 × 6.02214076 × 10^23 = 1.204 × 10^24 molecules. Conversely, 2 mol of water weighs 2 × 18.015 = 36.03 g.
Limitations — read this before you rely on it
This converts between mass, moles and particle counts only — it does not work out a molar mass from a chemical formula (a separate chemistry tool does that), and it assumes a pure substance. For solutions you also need concentration and volume, which this calculator does not cover.
Frequently asked questions
A mole is a counting unit: one mole of anything contains exactly 6.02214076 × 10^23 particles. It lets chemists count atoms and molecules by weighing them instead of counting them individually.
Divide the mass in grams by the substance's molar mass in g/mol. For example, 36.03 g of water ÷ 18.015 g/mol = 2 mol.
The mass of one mole of a substance, in grams per mole. It equals the sum of the atomic masses of the atoms in the formula — water (H₂O) is 2 × 1.008 + 16.00 = 18.015 g/mol.
Exactly 6.02214076 × 10^23, the number of particles in one mole. It is now a defined constant in the SI system, not a measured value.
Only for the pure-substance part. If you have a solution, you need its concentration (mol/L) and volume as well; moles = concentration × volume, and then this calculator's mass conversion still applies.