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Gibbs Free Energy Calculator
Enter the enthalpy change, entropy change, and temperature to calculate Gibbs free energy and see whether a process is spontaneous.
kJ/mol
J/(mol·K)
K
What This Calculator Does
This tool calculates the Gibbs free energy change (ΔG) for a process, which predicts whether that process will happen spontaneously at a given temperature.
The Formula
Gibbs free energy is found with ΔG = ΔH − TΔS, where ΔH is the enthalpy change (kJ/mol), T is the absolute temperature (K), and ΔS is the entropy change (J/(mol·K), converted to kJ/(mol·K) in the calculation to match units). A negative ΔG means the process is thermodynamically spontaneous as written; a positive ΔG means it is non-spontaneous (it would need outside energy input); a ΔG at or near zero means the system is at equilibrium.
A Few Notes
- Spontaneity here is a thermodynamic prediction only — it says a reaction is favorable, not how fast it will happen (that depends on kinetics, e.g. activation energy).
- Double-check that ΔH and ΔS are entered in the units this calculator expects (kJ/mol and J/(mol·K) respectively), since mixing them up is a common source of error.
- Intended for general chemistry education and planning purposes.
Last reviewed August 2026