Molarity is the concentration of a solution, measured as moles of solute per litre of solution (mol/L or M). A 2 M solution contains 2 moles of dissolved substance in every litre of solution. Molarity is the most widely used concentration measure in chemistry.

What is the molarity formula?

Molarity (M) equals moles of solute (n) divided by volume of solution in litres (V): M = n / V. Rearranged: moles equals molarity times volume (n = M x V), and volume equals moles divided by molarity (V = n / M).

How do I convert millilitres to litres for the molarity formula?

Divide the volume in millilitres by 1000 to get litres. For example, 250 mL is 0.25 L. The molarity formula requires volume in litres, so always convert before entering the value.

Molarity Calculator

This molarity calculator solves the relationship M = n / V, where M is the molarity in moles per litre, n is the moles of solute, and V is the volume of solution in litres, for whichever of the three quantities you do not know. Molarity is the most widely used way to express the concentration of a solution in chemistry and biology. A 2 M salt solution contains 2 moles of salt dissolved in every litre of solution. Knowing the molarity lets you immediately work out how much solute is in any volume, or how to make up a solution of a given strength, which is essential for titrations, buffer preparation, reagent dilution, and countless other laboratory procedures. You select which variable to solve for, enter the two known values, and the result appears straight away. To find molarity, the calculator divides moles by volume. To find moles needed, it multiplies molarity by volume. To find the volume of solution required, it divides moles by molarity. Volume must be in litres: divide millilitres by 1000 before entering. If you know the mass of solute in grams rather than the moles, first use the moles calculator by dividing mass by molar mass, and then enter the resulting moles here. The default example uses 0.50 mol dissolved to give 0.25 L of solution, which produces a molarity of 2.00 mol/L. This tool is designed for chemistry and biology students, laboratory scientists, and anyone preparing solutions for practical or industrial use. Results are mathematical and assume ideal solution behaviour.

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Solve for

Moles of solute (mol)

mol

Volume of solution (L)

Molarity (mol/L)

mol/L

2.00 mol/L

molarity

Molarity2.0000 mol/L

Moles of solute0.5000 mol

Volume0.2500 L

Volume must be in litres. Divide mL by 1000 before entering. To find moles from grams, use the Moles Calculator first.

How it works

The molarity formula is M = n / V. To find molarity: divide moles by volume in litres. To find moles: multiply molarity by volume (n = M x V). To find volume: divide moles by molarity (V = n / M). The selected variable's input row is hidden so you enter only the two known quantities. Division by zero is caught and an error message is displayed.

Worked example

You dissolve 0.50 mol of sodium chloride and make the solution up to a final volume of 0.25 L (250 mL). Molarity = 0.50 / 0.25 = 2.00 mol/L. This matches the default values pre-filled in the calculator above. To prepare 500 mL of 1.00 mol/L solution you would need 0.50 mol of solute.

Related calculators

Moles Calculator: convert between moles, mass, and molar mass.
Molar Mass Calculator: find the molar mass of any compound from its formula.
Dilution Calculator: calculate stock and diluent volumes using C1V1=C2V2.
pH Calculator: find pH from hydrogen ion concentration.

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