Molality Calculator

Calculate molality, solute amount or solvent mass with m = n / kg solvent.

Calculator

Molality uses the mass of solvent, not total solution volume: m = n / kg solvent.

Calculate
Molality1 mol/kg
Solute amount0.5 mol
Solvent mass0.5 kg

Formula and assumptions

m = n / kg solvent

Molality is based on the mass of solvent rather than the volume of solution, so it is useful when solution volume changes with temperature.

Assumption: The denominator is solvent mass, not total solution mass.

Variables and units

  • m — molality (mol/kg)
  • n — amount of solute (mol)
  • kg solvent — mass of solvent (kg)

Worked example

0.50 mol of solute dissolved in 0.50 kg of solvent gives a molality of 1.00 mol/kg.

Important limits

This does not calculate activity coefficients or account for chemical reactions.

Reference and related tools

IUPAC: molality. Return to Chemistry Calculators for the other tools in this group.