Molarity Calculator: M = mass / (molar mass x volume)

The concentration of a solution in moles per litre.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose which quantity you want to find.

Enter the other values in the units shown.

The calculator gives the answer with the formula, the substituted numbers, and the answer in other units.

Formulas used

  • M = \frac{m}{M_rV}
  • m = MM_rV

Worked example

With the default numbers in the calculator above:

  1. The formula, arranged to find the molarity: molarity = (mass of solute) / (molar mass of the solute x volume of the solution)
  2. Put the values in (every value in its SI unit): molarity = (5.844) / (58.44 x 0.5)
  3. The answer: molarity: 0.2 mol/L
  4. The same answer in other units: 200 mmol/L

Change the numbers in the calculator to see the full working, every step, for your own case.

Common questions

How do I calculate molarity?

Divide the mass of the solute by its molar mass to get the moles, then divide by the volume of the solution in litres.

How much solute do I weigh out for a given molarity?

Multiply the molarity by the molar mass and by the volume in litres.

What is the molarity of 5.844 g of NaCl in 0.5 L?

0.2 mol/L.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any chemistry text (molarity).

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