Enter the moles of the solute and the mass of the solvent to calculate the molality of that solution. This calculator can also determine either the moles or mass if the other values are known.

Molality Formula

The following formula is used to calculate molality.

Molality = N / M 
  • Where N is the number of moles of solute
  • and M is the mass of the solvent.

To calculate molality, divide the number of moles of solute by the mass of the solvent.

Molality Definition

Molality is described as the amount of solute divided by the mass of the solvent. Where the amount of solvent is measured in moles, and the mass of the solvent is measured in kg.

Molality is another way of conceptualizing the concentration of a solute to solvent in a solution. If you are unsure of the number of moles, you can visit our mole calculators. In simple terms, moles are the ratio of atoms to the mass of an atom of substance.

Molality is not to be confused with molarity. Molarity is a measure of concentration just like molality, but instead, it’s expressed as a unit per volume instead of a unit per mass like molality.

How to calculate molality?

How to calculate molality

  1. Choose your solute/subtance

    For example – H20

  2. Calculate the molar mass of that substance

    Visit the molar mass calculator

  3. Calculate the molar mass the moles

    Now you have the total number of moles of your solute

  4. Enter the moles calculated above and the mass of the solvent

    Now you have your molality of your concentration.


What is molality?

Molality is a measure of the number of moles of a solute to the mass of a solvent.

molality formula