Work out molarity from moles and volume, or solve a dilution with C1V1 = C2V2 — find whichever value is missing.
How to use this tool
Molarity turns moles and volume into a concentration; dilution finds the one missing value in C1V1 = C2V2.
Moles of solute and the total solution volume in litres — not the solvent volume alone.
Leave exactly one of C1, V1, C2, V2 blank and the calculator solves for it. V1 and V2 must share a unit.
Molarity comes out in mol/L (M). Dilution answers come out in the unit of the value solved for.
Formula & worked example
Dissolving 2 mol in 0.5 L gives 2 ÷ 0.5 = 4 M. Diluting: 2 M × 100 mL = 0.5 M × V2, so V2 = 200 ÷ 0.5 = 400 mL.
Limitations — read this before you rely on it
Molarity uses the final solution volume, not the volume of solvent added — dissolving solute changes the volume, so '2 mol in 0.5 L of water' is not the same as a 4 M solution. Dilution assumes the solute amount is unchanged (no reaction, precipitation or evaporation) and that volumes add simply, which breaks down for concentrated or non-ideal mixtures.
Frequently asked questions
Moles of solute per litre of solution, written M or mol/L. A 1 M solution contains 1 mole of solute in every litre of solution.
Use C1V1 = C2V2: the concentration times volume before dilution equals the same product after. Leave the unknown blank and the calculator rearranges the equation for you.
Yes — both in mL, or both in L. The concentrations must also share a unit. Mixing mL and L is the most common dilution mistake.
No. Moles are an amount; molarity is an amount per litre. Two litres of 1 M solution contain 2 moles, and so does one litre of 2 M solution.
Molarity is per litre of solution; molality is per kilogram of solvent. They are nearly equal in dilute water solutions but diverge for concentrated ones.