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Molarity Calculator

Find molarity, moles, mass, or solution volume from the values you know.

What do you want to use?

Enter a formula such as NaCl, H₂O, Ca(OH)₂, Al₂(SO₄)₃, or CuSO₄·5H₂O.

Molar mass: 58.440 g/mol

Use the volume of the finished solution, not the solvent volume.

Result

Molarity

0.400 M

400 mM

Moles
0.100 mol
Final solution volume
250 mL
Mass
5.844 g
Molar mass
58.440 g/mol

Examples

Calculation working

Calculate the molarity

  1. 1. Find the moles

    5.844 g ÷ 58.440 g/mol = 0.100 mol

  2. 2. Convert the final solution volume

    250 mL = 0.250 L

  3. 3. Molarity

    0.100 mol ÷ 0.250 L = 0.400 M

Important concept

Molarity uses the final solution volume

Molarity tells you how many moles of solute are present per liter of solution.

The volume is the final volume of the complete solution, not simply the amount of solvent you started with.

Molarity vs molality

Molarity

moles of solute / liters of solution

unit: mol/L or M

Molality

moles of solute / kilograms of solvent

unit: mol/kg

Molality has its own tool: the Molality Calculator.

The core relationship

M = n / V

M
= molarity in mol/L
n
= moles of solute
V
= final solution volume in liters

n = mass ÷ molar mass

M = mass ÷ (molar mass × final solution volume)

Scope

What this calculator handles

It handles:

  • Molarity
  • Moles
  • Mass
  • Final solution volume
  • Chemical-formula-based molar mass
  • Common mass and volume units
  • Step-by-step working

Use the Dilution Calculator for:

C₁V₁ = C₂V₂

FAQ

Frequently asked questions

What is molarity?

Molarity is the number of moles of solute per liter of solution. It is expressed in mol/L, commonly written as M.

How do I calculate molarity from mass?

First divide the mass by the molar mass to find moles. Then divide the moles by the final solution volume in liters. M = mass ÷ (molar mass × volume).

Do I use the solvent volume or solution volume?

Use the final volume of the solution. Molarity is based on the total solution volume after the solute has been added.

Can I calculate molarity from moles?

Yes. Divide the number of moles by the final solution volume in liters.

Can I calculate mass from molarity?

Yes. Multiply molarity × final solution volume × molar mass.

What does 1 M mean?

A 1 M solution contains 1 mole of solute per liter of solution.

Can I enter mL instead of L?

Yes. The calculator converts volume units automatically.

What is the difference between molarity and molality?

Molarity uses moles per liter of solution. Molality uses moles per kilogram of solvent.

Can I enter a chemical formula?

Yes. Enter a formula such as NaCl or Ca(OH)2 and the calculator can calculate its molar mass automatically.

Is molarity the same as concentration?

Molarity is one way to express concentration. It specifically means moles of solute per liter of solution.