Mole (mol) Calculator

The mole (mol) is the basic unit for amount of substance in chemistry, obtained by dividing mass by molecular weight (molar mass). It is the most fundamental concept for quantitative calculations in chemical reactions.

Enter a substance's mass (g) and molar mass (g/mol) to calculate the number of moles (mol). Molar mass can be found from the atomic weights in the periodic table or the molecular formula.

For example, 18 g of water (H₂O) has a molar mass of 18 g/mol, so the amount is 1 mol.

Mole (mol) Calculator Calculation Method

n: moles (mol), m: mass (g), M: molar mass (g/mol)

The amount (mol) is 0 .

About This Calculator

A mole is chemistry's counting unit: 6.022 × 10²³ particles, known as Avogadro's number. Converting a mass in grams into moles is the first step in almost every stoichiometry problem.

Enter the mass and the molar mass to get the number of moles, or enter mass and moles to find the molar mass.

Molar mass is the mass of one mole of a substance in grams per mole, numerically identical to its molecular weight. Water is 18.02 g/mol, sodium chloride 58.44 g/mol and glucose 180.16 g/mol. Dividing a weighed mass by the molar mass gives moles, which is the starting point of almost every stoichiometry calculation.

Key Formula:n (mol) = m (g) / M (g/mol)

Frequently Asked Questions

What is molar mass?

The mass of one mole of a substance in grams, numerically equal to its relative molecular mass. Water (H₂O) has a molar mass of about 18.02 g/mol, so 36.04 g of water is exactly 2 moles.

How do I find moles from concentration and volume?

Multiply molarity by volume in litres: n = C × V. Then convert to mass with m = n × M if you need grams, which chains this calculator to the molarity calculator.

How do I calculate molar mass from a formula?

Add the atomic masses of every atom in the formula. For H2SO4 that is 2 × 1.008 + 32.06 + 4 × 16.00 = 98.08 g/mol. Hydrates include the water of crystallisation: CuSO4·5H2O is 249.7 g/mol.

What is the difference between molar mass and molecular weight?

Molecular weight is dimensionless and expressed in atomic mass units; molar mass is the same number in grams per mole. For laboratory work the two are interchangeable.

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Sources & last update

2026-10-19