Mole Fraction Calculator

About this calculator

Mole fraction expresses the composition of a mixture as xᵢ = nᵢ / n_total — the moles of one component divided by the total moles of all components in the mixture. Unlike mass percent or molarity, it's a dimensionless ratio that always sums to 1 across every component, which makes it the natural unit for describing gas and liquid mixtures in thermodynamic equations.

Chemists and chemical engineers rely on mole fraction in Raoult's law (a component's vapor pressure equals its mole fraction times the pure-liquid vapor pressure) and Dalton's law of partial pressures (partial pressure equals mole fraction times total pressure), both central to distillation design, phase-equilibrium calculations, and gas-mixture analysis. Students use it in stoichiometry and physical chemistry labs whenever a problem calls for composition independent of volume or mass.