Molarity Calculator (Moles per Litre)
Find the molarity of a solution directly from the moles of solute and the solution volume in litres.
How it works
molarity M = moles of solute ÷ volume of solution (litres)
Molarity is the most common way chemists state concentration: the number of moles of solute dissolved per litre of the final solution. This version starts from moles you already know and simply divides by the solution volume. Always use the total volume of the finished solution, not the volume of solvent you began with.
Worked example
Dissolving 0.5 mol of solute and making the volume up to 1 L gives 0.5 ÷ 1 = 0.5 mol/L, a 0.5 M solution.
Sources: Molar concentration — Wikipedia
Frequently asked questions
How is molarity different from molality?
Molarity is moles per litre of solution and changes slightly with temperature as the volume expands. Molality is moles per kilogram of solvent and is temperature-independent, which matters for precise colligative-property work.
What if I only know the mass of solute?
Convert the mass to moles first by dividing by the molar mass, then use that mole figure here. The grams-to-moles calculator does that conversion.
Does the volume have to be in litres?
Yes for the answer to come out in mol/L. If you measured in millilitres, divide by 1,000 first — 250 mL is 0.25 L.
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