Molarity / Dilution Calculator

Molarity (M) is moles of solute per liter of solution. A 4 M solution contains 4 moles of dissolved substance in every liter — it measures how crowded the solute particles are.

Divide moles of solute by liters of solution: M = n / V. Dissolving 2 moles in 0.5 L gives 2 ÷ 0.5 = 4 M. This calculator also rearranges the formula to solve for moles (n = M × V) or volume (V = n / M).

Diluting a solution adds solvent but no solute, so the moles before and after are equal: M1 × V1 = M2 × V2. Given any three of the four values, the equation finds the fourth — for example, diluting 10 mL of 6 M stock to 100 mL gives 6 × 10 ÷ 100 = 0.6 M.

Molarity is moles per liter of solution; molality is moles per kilogram of solvent. Molality doesn't change with temperature (liquids expand and contract), so it's preferred for precise physical chemistry, but molarity is the standard in most lab work.

They just have to be consistent — both in mL or both in L — because the units cancel on each side. This calculator converts units for you, so you can freely mix mL with L.

Molarity counts particles (moles), not mass. Convert grams to moles first by dividing by the substance's molar mass — the Molecular Weight Calculator on this site does that step.