Moles to Grams Calculator

Type a formula or molar mass. Convert grams, moles and molecules.

To convert grams to moles, divide the mass by the molar mass: n = m / M. To convert moles to grams, multiply: m = n × M. Multiply moles by Avogadro's number, 6.02214076 × 10²³ mol⁻¹, to get the number of molecules. For example, 10 g of NaCl (M = 58.44 g/mol) is 0.1711 mol, or 1.030 × 10²³ formula units.

Free, runs in your browser. Nothing you enter is uploaded.

What you enter

Chemical formula (parentheses, brackets and hydrates allowed) or molar mass in g/mol
Mass, moles or number of particles

What you get

Molar mass with element-by-element breakdown and mass percent
Mass, moles and number of particles
Step-by-step working

Formula

n = m / M   |   m = n × M   |   N = n × Nᴀ,  Nᴀ = 6.02214076 × 10²³ mol⁻¹

The molar mass M is the sum of the standard atomic weights of every atom in the formula, including water of crystallisation in hydrates. Avogadro's constant has been exact since the 2019 SI redefinition.

Questions

How do you convert grams to moles?

Divide the mass in grams by the molar mass in g/mol. For 25 g of water, 25 ÷ 18.015 = 1.388 mol.

How do you convert moles to grams?

Multiply the number of moles by the molar mass. 0.5 mol of NaCl is 0.5 × 58.44 = 29.22 g.

How do you convert moles to molecules?

Multiply moles by Avogadro's number, 6.02214076 × 10²³. So 2 mol of CO2 contains 1.204 × 10²⁴ molecules.

How do I enter a hydrate?

Use a middle dot, an asterisk or a full stop before the water, for example CuSO4·5H2O, CuSO4*5H2O or CuSO4.5H2O. The water molecules are included in the molar mass.

Why is my molar mass slightly different from the bottle label?

Suppliers often use older or more precise atomic weights, so values can differ in the second decimal place. The difference is well under 0.1 % and does not matter for normal lab work.

References

More Chemistry

All free tools · By Dr. Zubair Khalid, DVM, MS, PhD.