Gibbs Free Energy Calculator

Summary

The Gibbs Free Energy Calculator computes ΔG using the fundamental thermodynamic equation ΔG = ΔH − TΔS, where ΔH is the enthalpy change, T is the absolute temperature in Kelvin, and ΔS is the entropy change. A negative ΔG indicates a spontaneous reaction, a positive ΔG indicates a non-spontaneous reaction, and ΔG = 0 signals the system is at equilibrium. All calculations are performed entirely in your browser with no data sent to any server.

How it works

1. Enter the enthalpy change (ΔH) in kilojoules per mole (kJ/mol).
2. Enter the temperature in Kelvin (K) or switch to Celsius — the tool converts automatically.
3. Enter the entropy change (ΔS) in joules per mole per Kelvin (J/mol·K).
4. Click Calculate; the tool applies ΔG = ΔH − TΔS (converting ΔS from J to kJ internally).
5. Review the result: sign, magnitude, spontaneity verdict, and a plain-language explanation.
6. Use the Reset button to clear all fields and start a new calculation.

Use cases

• Determine whether a chemical reaction will proceed spontaneously under given conditions.
• Solve thermodynamics problems in general chemistry and physical chemistry courses.
• Find the crossover temperature at which a reaction switches from spontaneous to non-spontaneous.
• Verify hand-calculated ΔG values for lab reports or homework assignments.
• Analyze industrial reactions to predict feasibility without running the experiment.
• Study the interplay between enthalpy and entropy in driving chemical processes.
• Prepare for AP Chemistry, university thermodynamics, or graduate-level physical chemistry exams.

Frequently Asked Questions