Gibbs Free Energy Calculator
Calculator
\[ \Delta G = \Delta H - T\Delta S \qquad \Delta G^\circ = -RT\ln K \]
where ΔG, ΔH, ΔS, T, K, and R denote, respectively, the Gibbs free energy change (J/mol), enthalpy change (J/mol), entropy change (J·mol⁻¹·K⁻¹), temperature (K), equilibrium constant, and the gas constant (8.314 J·mol⁻¹·K⁻¹).
Gibbs Free Energy Calculator
Result
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Gibbs Energy/Equilibrium Constant Converter
\[ \Delta G^\circ = -RT\ln K \]
Spontaneity Summary
ΔH ΔS Spontaneity
− (exothermic)+ (disorder increases)Spontaneous at all temperatures
+ (endothermic)− (disorder decreases)Never spontaneous
− (exothermic)− (disorder decreases)Spontaneous at low T (below ΔH/ΔS)
+ (endothermic)+ (disorder increases)Spontaneous at high T (above ΔH/ΔS)
About This Tool

Gibbs free energy G combines enthalpy and entropy into a single criterion for spontaneity at constant temperature and pressure: ΔG = ΔH − TΔS. A negative ΔG indicates a spontaneous process, a positive ΔG indicates a non-spontaneous one, and ΔG = 0 marks the point of equilibrium. This calculator lets you solve for any one of ΔG, ΔH, ΔS, or T given the other three. Note that ΔH is entered in kJ/mol while ΔS is in J·mol⁻¹·K⁻¹ — the calculator handles the unit conversion automatically. The crossover temperature T = ΔH/ΔS is the temperature at which ΔG changes sign, indicating the boundary between spontaneous and non-spontaneous conditions. The second section converts between the standard Gibbs free energy ΔG° and the equilibrium constant K using ΔG° = −RT·ln(K), which is fundamental to chemical equilibrium, electrochemistry, and thermodynamic cycle analysis.