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Molarity Calculator

Molarity Calculator is part of Toolspire and is ready as soon as this page loads. The volume is the volume of the solution, not the volume of the solvent you poured in before the solute took up space. Units are moles and litres.

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Moles of soluteLitres of solution

Result

0.25 mol/L

0.5 mol in 2 L of solution.

A classroom concentration. It does not look up a molar mass, so grams must be converted to moles first.

On this page

What you can do here

Moles in, not grams

There is no molar-mass box. Convert mass ÷ molar mass before you arrive.

Litres of solution

The label says solution so a solvent-only volume is a known shortcut, not what the definition asks.

0.25 is the check

Half a mole in two litres is a quarter molar.

The sequence

How to use the Molarity Calculator

1
Convert grams to moles first
Moles = mass ÷ molar mass. 58.44 g of NaCl is about 1 mole, not 58.44 moles.
2
Convert millilitres to litres
Divide by 1,000.
3
Check 0.25
0.5 divided by 2.

Worth knowing

Molarity Calculator on Toolspire: molarity = moles ÷ litres.
0.5 mol ÷ 2 L = 0.25 mol/L.
Millilitres must be divided by 1,000 before you type them. 500 mL is 0.5 L.
A volume of zero is rejected.

Concentration is amount over solution volume

Molarity is how many moles are dissolved in one litre of the finished solution. Half a mole spread through 2 litres is 0.25 mol/L. The page will not divide by a molar mass and will not accept millilitres as if they were litres. A dilution, where you already know a concentrated stock, is the next page: C1V1 = C2V2.

FAQ

Questions about Molarity Calculator

Where does Molarity Calculator run?

Molarity Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What is the molarity of 0.5 mol in 2 L?

0.25 mol/L.

Can I type grams?

Not directly. Divide the mass by the molar mass and type the moles.

What about 500 mL?

Type 0.5 litres.

Is this molality?

No. Molality is moles per kilogram of solvent. This is moles per litre of solution.

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Last updated 23 October 2026Report a problem or suggest a feature