Molarity Calculator – Formula & Examples

About the Molarity Calculator

Molarity is the number of moles of solute per litre of solution. Enter the formula and this calculator handles the grams-to-moles step for you, so you can go straight from a weighing to a concentration, or work backwards to find the mass you need to weigh out.

Also known as: molar concentration, mol/l calculator, concentration calculator, m concentration, molarity from grams.

How to use this calculator

Enter solve for, solute formula and the other fields.
The result updates instantly as you type — press Calculate (or Enter) at any time.
Open “Step-by-step” to see how the answer was worked out.
Use Copy result or Share to save the answer or send a link with your inputs.

Formula

M = moles of solute ÷ litres of solution

Worked example

Using the values pre-filled in the calculator above:

Solve for: Molarity
Solute formula: NaCl
Mass of solute = 58.44 g
Solution volume = 1 L

the calculator returns:

Molarity: 1 mol/L
Moles of solute: 1 mol
Molar mass: 58.44 g/mol
Millimolar: 1,000 mM

Working

n = 58.44 g ÷ 58.44 g/mol = 1 mol
M = 1 mol ÷ 1 L = 1 mol/L

Frequently asked questions

What is the difference between molarity and molality?

Molarity uses the volume of the whole solution; molality uses the mass of the solvent only, so it does not change with temperature.

Do I dissolve in 1 litre of water?

No — dissolve the solute in less water, then top up to the 1 litre mark. Molarity is per litre of solution, not per litre of solvent.

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