This molarity calculator helps you make up solutions. Find the mass of solute to weigh out for a target concentration, the molarity of a solution you have made, or the volume needed. Common lab chemicals are built in, or enter any molar mass.
Molarity formulas
Molarity (M) = moles of solute ÷ litres of solution
Moles = mass (g) ÷ molar mass (g/mol)
So the mass needed is: mass = molarity × volume (L) × molar mass.
Worked example
To make 1 litre of 0.5 M sodium chloride (molar mass 58.44 g/mol), you need 0.5 × 1 × 58.44 = 29.22 g of NaCl. Dissolve it in less than a litre of water, then add water up to exactly 1 litre.
Molarity units
- 1 M = 1 mol/L
- 1 mM (millimolar) = 0.001 M
- 1 µM (micromolar) = 0.000001 M
Molarity is different from molality (moles per kilogram of solvent), which does not change with temperature.
Frequently asked questions
What is the difference between molarity and molality?
Molarity is moles per litre of solution; molality is moles per kilogram of solvent. Molarity changes slightly with temperature because volume changes, while molality does not.
How do I find a molar mass?
Add the atomic masses of every atom in the formula. For NaCl: sodium 22.99 + chlorine 35.45 = 58.44 g/mol.
How do I dilute a solution?
Use C₁V₁ = C₂V₂: the starting concentration times the volume you take equals the final concentration times the final volume.
Should I use the volume of water or of the solution?
The final volume of the solution. Adding the solute to exactly 1 L of water gives slightly more than 1 L of solution.
Related calculators
Last reviewed: October 2026.