Clausius–Clapeyron Calculator

About this calculator

The Clausius–Clapeyron equation, ln(P₂/P₁) = −ΔHvap/R × (1/T₂ − 1/T₁), links a liquid's vapor pressure at two different temperatures through its molar enthalpy of vaporization. Because vapor pressure rises steeply — and roughly exponentially — with temperature, knowing it at one reference point lets you predict it at another without a new measurement.

Chemists and chemical engineers use it to predict boiling points at non-standard pressures, size distillation columns, and read vapor-pressure charts used in solvent selection; it also explains why water boils at a lower temperature on a mountaintop and shows up in meteorology when relating dew point to humidity. Culinary science even borrows it to explain why recipes need adjusting at altitude.