Gibbs Free Energy Calculator
Compute ΔG = ΔH − TΔS and instantly see whether a reaction is spontaneous, non-spontaneous, or at equilibrium.
Use the Gibbs Free Energy Calculator
Inputs
K
°C + 273.15 = K | standard = 298.15 K
Enter values and click Calculate to see ΔG
Gibbs Free Energy Change
—
kJ/mol
Step-by-step derivation
Sign interpretation
ΔG < 0
Spontaneous (exergonic) — reaction proceeds without external energy.
ΔG = 0
At equilibrium — no net driving force in either direction.
ΔG > 0
Non-spontaneous (endergonic) — requires energy input to proceed.
Summary
The Gibbs Free Energy Calculator applies the fundamental relation ΔG = ΔH − TΔS to determine whether a reaction is spontaneous at a given temperature. Enter the enthalpy change (ΔH), temperature (T in kelvin), and entropy change (ΔS) in your preferred units. The tool converts everything to consistent SI units, computes ΔG, and reports the spontaneity verdict alongside a step-by-step derivation.
How it works
- Enter the enthalpy change (ΔH) with its unit (kJ/mol, kcal/mol, or J/mol).
- Enter the absolute temperature (T) in kelvin.
- Enter the entropy change (ΔS) with its unit (J/(mol·K) or cal/(mol·K)).
- Click Calculate — the tool applies ΔG = ΔH − TΔS and converts all inputs to consistent SI units first.
- Read the ΔG value and the spontaneity verdict: negative ΔG = spontaneous, positive = non-spontaneous, zero = equilibrium.
- Use the unit selector to view ΔG in kJ/mol, kcal/mol, or J/mol.
Use cases
- Determine whether a chemical reaction will occur spontaneously at a given temperature.
- Find the temperature crossover point where a reaction switches from spontaneous to non-spontaneous.
- Check thermodynamics homework problems with a step-by-step breakdown.
- Verify ΔG calculations for biochemical reactions (ATP hydrolysis, metabolic pathways).
- Explore how entropy and enthalpy contributions change with temperature.
- Support physical chemistry coursework and exam preparation.
Frequently Asked Questions
Last updated: 2026-06-11 · Reviewed by Nham Vu