Equilibrium Constant Calculator

About this calculator

This calculator finds the equilibrium constant K of a chemical reaction from its Gibbs free energy change using K = exp(−ΔG°/RT), the rearranged form of the thermodynamic relation ΔG° = −RT·ln(K), where R is the gas constant (8.314 J/mol·K) and T is the absolute temperature. This equation is the bridge between thermodynamics and chemical equilibrium: a large negative ΔG° (a thermodynamically favorable reaction) produces a K much greater than 1, meaning the equilibrium lies far toward products, while a positive ΔG° gives K less than 1, favoring reactants.

Chemistry students and researchers use this to connect free-energy data from tables to predicted reaction extent; chemical engineers use it when designing reactors to predict how far a reaction will proceed under given conditions; and biochemists use the same relationship to study equilibria in enzyme reactions, ligand binding, and protein folding. Enter the Gibbs free energy change and temperature to get the equilibrium constant.