Calculate the molarity of a solution from moles or mass and volume.
Calculated instantly in your browser.
How do you calculate the molarity of a solution?
Molarity (M) = moles of solute ÷ litres of solution; to get moles from a mass, divide the mass by the molar mass. Molarity measures concentration as moles of solute per litre of solution, not per litre of solvent. For example, dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in 1 litre gives 1 mole in 1 L = 1 M.
Understanding your result
Molarity measures concentration as moles of solute per litre of solution (not per litre of solvent). It is the most common concentration unit in chemistry for reactions and titrations.
Formula and method
Molarity (M) = moles of solute ÷ litres of solution. To get moles from a mass, divide the mass by the molar mass.
Assumptions and limitations
This tool assumes a fully dissolved, homogeneous solution and that volume is measured for the final solution, not the solvent added. It does not account for volume changes on mixing, temperature effects on volume, dissociation into ions, hydrated salts or purity below 100%. Use the correct anhydrous molar mass for accurate results.
Worked example
Dissolving 58.44 g of NaCl (molar mass 58.44 g/mol) in 1 litre gives 1 mole in 1 L = 1 M.
How to use this tool
- Choose to enter moles, or mass and molar mass.
- Enter the solution volume and unit.
- Read the molarity in mol/L.
Common mistakes to avoid
- Using the volume of solvent instead of the final solution.
- Forgetting to convert millilitres to litres.
About the Molarity Calculator
The Molarity Calculator finds the concentration of a solution in moles per litre. Enter the moles of solute — or the mass and molar mass — and the solution volume to get the molarity.
Who should use this tool
Chemistry students and lab workers preparing or analysing solutions.
Benefits
- Molarity from moles or from mass.
- Volume in litres or millilitres.
- Shows the moles and the working.
- Pairs with the Molar Mass Calculator.
Practical use cases
- Preparing a solution at a target concentration.
- Working out the molarity from a weighed sample.
- Checking a titration calculation.
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Frequently asked questions
What is molarity?
The number of moles of dissolved solute per litre of solution, written as M (mol/L).
How do I get moles from grams?
Divide the mass in grams by the molar mass in g/mol. Use the Molar Mass Calculator to find a compound’s molar mass.
Is molarity the same as molality?
No. Molarity is moles of solute per litre of solution, while molality is moles of solute per kilogram of solvent. Molality does not change with temperature because it uses mass, whereas molarity shifts slightly as volume expands or contracts. This calculator computes molarity only.