Molality Calculator Formula

Understand the math behind the molality calculator. Each variable explained with a worked example.

Use the Molality Calculator

Formulas Used

Molality

molality = moles_solute / mass_solvent_kg

Variables

VariableDescriptionDefault
moles_soluteMoles of Solute(mol)0.5
mass_solvent_kgMass of Solvent(kg)1

How It Works

How to Calculate Molality

Formula

m = n / w

Where:

  • m = molality (mol/kg)
  • n = moles of solute
  • w = mass of solvent in kilograms

    • Molality does not change with temperature because mass is temperature-independent.

    Worked Example

    Dissolve 0.5 moles of glucose in 1 kg of water.

    moles_solute = 0.5mass_solvent_kg = 1
    1. 01m = n / w
    2. 02m = 0.5 mol / 1 kg
    3. 03m = 0.5 mol/kg

    Ready to run the numbers?

    Open Molality Calculator