Molarity Calculator
Fill in any two of molarity, moles of solute and volume of solution, leave the third blank, and this calculator solves for it.
Molarity = moles of solute ÷ litres of solution. Leave any one field blank and the calculator solves for it from the other two.
How to calculate molarity by hand
- Find the moles of solute — convert from mass using moles = mass ÷ molar mass if you only have grams.
- Find the volume of the final solution in litres (convert from mL by dividing by 1000).
- Divide: molarity = moles ÷ litres.
Worked example
Dissolving 58.5 g of NaCl (molar mass 58.5 g/mol, so 1 mol) in enough water to make 500 mL (0.5 L) of solution gives a molarity of 1 ÷ 0.5 = 2 mol/L.
Find a compound's molar mass first in the Molar Mass Calculator, then mix real solutions and watch reactions happen in the Chemistry Lab.
Frequently asked questions
How do you calculate molarity?
Divide the moles of solute by the volume of solution in litres: M = mol ÷ L. Dissolving 0.5 mol of solute in 2 L of solution gives a molarity of 0.25 mol/L.
What is molarity measured in?
Moles per litre (mol/L), also written as M. A "1 M" solution has 1 mole of solute per litre of solution.
How do you find moles from molarity?
Rearrange the formula to moles = molarity × volume (in litres). A 0.5 M solution in 3 L contains 0.5 × 3 = 1.5 mol of solute.
Does molarity use the volume of solvent or of the whole solution?
The whole solution, after the solute has been dissolved and the volume made up — not just the volume of water added before it.
