Molarity calculator

Choose what to find, enter the rest and read the answer. The box for the quantity you solve for is ignored. Get the molar mass from a formula with the molar mass calculator, and use the dilution calculator when you add solvent to a stock solution.

Solve for

Mass of solute (g)

Molar mass (g/mol)For example NaCl is 58.44 g/mol. Look up a formula with the molar mass calculator.

Volume of solution

Volume unit

Molarity (mol/L)

Molarity0.1 mol/L

Mass of solute: 5.844 g
Volume of solution: 1 L
Amount of solute: 0.1 mol
Molarity in mmol/L: 100 mmol/L

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How to use it

Choose to solve for molarity, the mass of solute or the volume.
Enter the other values and the molar mass of the solute in g/mol.
Read the result, together with the number of moles and the molarity in mmol/L.

How it works

Moles are n = mass ÷ molar mass, and molarity is M = n ÷ V with V in litres. The solved forms are mass = M × V × molar mass and V = mass ÷ (molar mass × M).

Worked example

5.844 g of sodium chloride (58.44 g/mol) is 0.1 mol. Dissolved to a volume of 1 L, the molarity is 0.1 mol/L.

Tips

Use the molar mass of the exact form you weigh, such as a hydrate, not the anhydrous salt.
Keep volumes in the final solution, not the amount of water you add.

Frequently asked questions

What is molarity?

Molarity (M) is the amount of dissolved substance in moles per litre of solution: M = n ÷ V. A 1 M solution holds one mole of solute in every litre of finished solution.

How much solute do I weigh to make a solution?

Choose Mass of solute and enter the molarity, molar mass and the final volume. For 250 mL of 0.5 M with a molar mass of 40 g/mol, the mass is 0.5 × 0.25 × 40 = 5 g.

Is the volume the solvent or the final solution?

The final solution. Dissolve the solute in less solvent, then top up to the final volume mark, for instance in a volumetric flask.

What about molality or percent concentration?

Molality is moles per kilogram of solvent and mass percent is a ratio of masses, so they need other formulas. This tool covers molarity only.

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All tools in this category: Education ·Updated November 3, 2026