Molarity is the number of moles of a solute per litre of solution. Use this calculator to find the concentration of a solution, or work out how many grams of a substance to weigh out for a target concentration and volume.
Formula
M = m / (MW × V)
Where M is the molarity (mol/L), m is the mass of solute (g), MW is the molar mass (g/mol), V is the volume of solution (L).
Choose any value to calculate — the calculator rearranges the formula for you.
Worked example
To make 1 L of 0.5 M sodium chloride (NaCl, molar mass 58.44 g/mol) you need 0.5 × 58.44 × 1 = 29.22 g of NaCl, dissolved and topped up to 1 L.
Finding the molar mass
Add up the atomic masses of every atom in the formula. NaCl = 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol.
Frequently asked questions
What is the unit of molarity?
Moles per litre (mol/L), written M. A 2 M solution has 2 moles of solute in every litre of solution.
What is the difference between molarity and molality?
Molarity is moles per litre of solution; molality is moles per kilogram of solvent. Molality does not change with temperature.
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