Molarity Calculator

In short: Compute molarity from mass, molecular weight, and solution volume. It is free, works in your web browser and needs no download.

Compute solution molarity from solute mass, molecular weight, and final solution volume.

How molarity is calculated

Molarity (M) is moles of solute per litre of solution: M = (mass in g ÷ molecular weight in g/mol) ÷ volume in L. The calculator converts your volume from mL to L for you. Example: 1.50 g of NaCl (58.44 g/mol) in 250 mL gives 0.02567 mol ÷ 0.250 L = 0.103 M.

Use the final volume of the whole solution, not the volume of solvent added. Molarity changes slightly with temperature because volume does; if you need a temperature-independent value, use molality instead.

Molarity versus molality: molarity divides by litres of solution, molality by kilograms of solvent. For dilute aqueous solutions near room temperature the two numbers are close, but they diverge for concentrated solutions or other solvents. Units: 1 M = 1 mol/L = 1000 mM. To dilute a stock you have made, continue with the dilution calculator.