Molality Calculator

Molality (m) is concentration measured in moles of solute per kilogram of solvent (mol/kg). A 1 m solution has 1 mole of solute dissolved in 1 kilogram of solvent (not solution).

Molarity (M) is moles per liter of solution and is volume-based. Molality is moles per kilogram of solvent and is mass-based. Molality does not change with temperature, while molarity does because the solution volume expands or contracts.

For colligative properties (boiling-point elevation, freezing-point depression, vapor-pressure lowering, osmotic considerations in some contexts), use molality. For most other intro chemistry problems, molarity is more common.

Molality uses only the solvent's mass. That makes the unit temperature-independent and decouples it from solute-driven volume changes. Molarity, by contrast, depends on the total solution volume.

Yes. Switch the solute input to 'Grams + molar mass'. The calculator converts grams to moles using n = m / M, then plugs into the molality formula.

Molality in mol/kg, also written 'm' (lowercase italic in formal notation). 1 m solution is read as 'one molal' to avoid confusion with 1 M (one molar).