Grams to Moles Calculator
Convert grams to moles or moles to grams. Type a formula like NaCl and the molar mass is worked out for you, or enter a molar mass yourself.
- Both directions
- Molar mass from a formula
- Particle count
- Free
Convert mass and moles
Case matters: Co is cobalt, CO is carbon monoxide. Brackets and hydrates work, e.g. Ca(OH)2 or CuSO4·5H2O.
The mass of one mole, in grams per mole. It must be more than zero.
A negative amount is not a real quantity, so it is not accepted.
Show the working
How to convert grams to moles
Find the molar mass
Add up the atomic masses in the formula. NaCl is 22.990 + 35.45 = 58.44 g/mol.
Divide the grams by it
10 g ÷ 58.44 g/mol = 0.1711 mol. The grams cancel and moles are left.
Going back is a multiply
Moles to grams runs the other way: 0.1711 mol × 58.44 g/mol = 10 g.
A mole is just a count, like a dozen: 6.02214076 × 10²³ particles of anything. The molar mass is the bridge between that count and a mass you can weigh out.
Questions people ask
How do you convert grams to moles?
Divide the mass in grams by the molar mass in grams per mole. 10 g of table salt (NaCl, 58.44 g/mol) is 10 ÷ 58.44 = 0.171 mol.
How do you convert moles to grams?
Multiply the number of moles by the molar mass. 0.25 mol of water (18.015 g/mol) is 0.25 × 18.015 = 4.50 g.
What is a mole in chemistry?
A counting unit, like a dozen but much bigger: one mole is 6.02214076 × 10²³ particles. That number, the Avogadro constant, is exact by definition. A mole of any substance contains the same number of particles; what changes is how much it weighs.
Where do I find the molar mass?
Add the standard atomic weight of every atom in the formula. This calculator does it for you when you type the formula, and the molecular weight calculator shows the full breakdown element by element.
Is molar mass the same as molecular weight?
The number is the same. Molecular weight is a ratio and has no units; molar mass is that number in grams per mole. Water is 18.015 either way.
How many molecules are in my sample?
Multiply the moles by 6.02214076 × 10²³. Half a mole of water is about 3.01 × 10²³ molecules. The calculator shows this as the particle count. For something ionic like NaCl the particles are formula units rather than molecules, because a salt crystal is a lattice and not a collection of separate NaCl molecules.
Why does it refuse a negative mass?
Because there is no such thing as negative grams of a substance. If you are working out a change in mass, convert the size of the change and add the direction yourself.
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