Molarity is the concentration of a solution in moles of solute per litre of solution, with the unit M or mol per litre. A 2 molar solution has 2 moles of solute in every litre.

What is the molarity formula?

Molarity equals moles of solute divided by litres of solution. Rearranged, moles equals molarity times litres, and litres equals moles divided by molarity.

How do I get moles from a mass?

Divide the mass in grams by the molar mass in grams per mole using the moles calculator, then use that result here as the moles of solute.

Molarity Calculator

This molarity calculator works with the relationship that molarity equals moles of solute divided by litres of solution, and lets you solve for whichever of the three quantities you do not know. Molarity is the most widely used measure of concentration in chemistry, written with the unit M or mol per litre, and it tells you how much dissolved substance sits in each litre of solution. A 2 molar salt solution, for example, contains 2 moles of salt in every litre. You choose what you want to solve for, the molarity, the moles of solute or the volume of solution, then enter the other two values and the calculator returns the answer. To find concentration, it divides the moles by the litres; to find the moles needed, it multiplies the molarity by the litres; and to find the volume, it divides the moles by the molarity. Volume here is in litres, so convert millilitres by dividing by 1000 first. If you know the mass of solute rather than the moles, work out the moles first with the moles calculator by dividing the mass by the molar mass, then bring that figure here. This is everyday bench chemistry, essential for making up solutions and standardising titrations. Enter your known values to see the result straight away.

Solve for

Molarity (mol/L)

Moles of solute

Volume (L)

2 mol/L

molarity

Volume is in litres; divide millilitres by 1000. Estimate only.

How it works

The calculator uses molarity equals moles over litres. To find molarity it divides moles by volume, to find moles it multiplies molarity by volume, and to find volume it divides moles by molarity. The quantity you are solving for is hidden so you only enter the two you know.

Worked example

Dissolving 0.5 moles of solute and making the solution up to 0.25 litres gives a molarity of 0.5 over 0.25, which is 2 moles per litre, a 2 molar solution.

Related calculators

Moles Calculator: mass to moles.
Molar Mass Calculator: molar mass.
Dilution Calculator: dilute a stock.
pH Calculator: acidity.

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