Molarity Calculator
Calculate molarity (moles per litre) from the amount of solute and the volume of solution.
How it works
M = moles of solute / litres of solution
Molarity is the most common way to state concentration: the number of moles of dissolved solute per litre of the final solution. A 1 mol/L (1 M) solution contains one mole of solute in every litre. Note that the volume is the total solution volume, not the volume of solvent added.
Worked example
Dissolving 0.5 mol of salt to make 2 L of solution gives a molarity of 0.5 ÷ 2 = 0.25 mol/L.
Frequently asked questions
What is the difference between molarity and molality?
Molarity divides moles by litres of solution, so it changes slightly with temperature. Molality divides moles by kilograms of solvent and is temperature-independent.
Does molarity use solvent or solution volume?
The total solution volume after mixing. Adding solute can change the volume, so you measure the final volume rather than the solvent alone.
How do I get moles from grams?
Divide the mass in grams by the substance’s molar mass in g/mol. For example, 58.5 g of NaCl is 1 mol because its molar mass is 58.5 g/mol.
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