Molality Calculator

Calculate molality (moles of solute per kilogram of solvent). Unlike molarity, molality is independent of temperature.

🧪 MOLES OF SOLUTE

mol

💧 MASS OF SOLVENT

MOLALITY

1 mol/kg (m)

FORMULA

m = mol_solute / kg_solvent

💡 How to Calculate Molality

What Is Molality?

Molality (m) is a measure of the concentration of a solution expressed as the number of moles of solute per kilogram of solvent. Unlike molarity (which uses volume of the total solution), molality uses the mass of the solvent only.

Because mass does not change with temperature, molality is temperature-independent, making it the preferred concentration unit for colligative property calculations.

How to Calculate Molality

Molality Formula

m = mol_solute / kg_solvent

Where m is molality in mol/kg, mol_solute is the number of moles of solute, and kg_solvent is the mass of the solvent in kilograms.

Molality vs. Molarity

Molarity (M) = moles of solute / liters of solution. Molality (m) = moles of solute / kilograms of solvent. The key difference is that molarity depends on volume (which changes with temperature), while molality depends on mass (which remains constant). For dilute aqueous solutions at room temperature, molality and molarity are approximately equal.