About this calculator
Switch to the second mode to find how many grams to weigh out for a solution you want to prepare.
How to use it
- Enter the solute formula or molar mass.
- Enter the mass and volume, or the target molarity.
- Read the result.
The formula
M = moles of solute ÷ litres of solution; mass = M × V × molar mass
- M
- molarity in mol/L
- V
- volume of solution in litres
Worked example
5.844 g of NaCl in 250 mL
- Moles = 5.844 ÷ 58.44 = 0.1 mol.
- M = 0.1 ÷ 0.25 L = 0.4 M.
What the result means
Molarity uses the volume of the whole solution, not of the solvent added.
Assumptions
- Solute fully dissolved.
Limitations
- Molarity changes slightly with temperature, as volume does; molality does not.
Frequently asked questions
What is the difference between molarity and molality?
Molarity is per litre of solution; molality is per kilogram of solvent.
How do I make a 1 M NaCl solution?
Dissolve 58.44 g of NaCl and make up to 1 litre.
What is mM?
Millimolar: one thousandth of a mole per litre.
Last reviewed on 6 October 2026. Found a mistake? Tell us.