Gibbs Free Energy Calculator

Calculate Gibbs free energy change (ΔG) from enthalpy (ΔH), entropy (ΔS), and temperature (T) for chemical reactions.

Enthalpy Change (ΔH)

Entropy Change (ΔS) in J/(mol·K)

Temperature (T) in K

Result

Please check your inputs.

Enter the enthalpy change (ΔH) for your reaction in kilojoules per mole (kJ/mol). Enter the entropy change (ΔS) in joules per mole-kelvin (J/(mol·K)). Enter the temperature (T) in Kelvin (K) — make sure to convert from Celsius if needed. Click 'Calculate' to instantly get the Gibbs free energy change (ΔG) in kJ/mol. Interpret the result — a negative ΔG means the reaction is spontaneous under the given conditions; positive means non-spontaneous; zero means equilibrium.

📖 How to Use This Tool

Enter the enthalpy change (ΔH) for your reaction in kilojoules per mole (kJ/mol).

Enter the entropy change (ΔS) in joules per mole-kelvin (J/(mol·K)).

Enter the temperature (T) in Kelvin (K) — make sure to convert from Celsius if needed.

Click 'Calculate' to instantly get the Gibbs free energy change (ΔG) in kJ/mol.

Interpret the result — a negative ΔG means the reaction is spontaneous under the given conditions; positive means non-spontaneous; zero means equilibrium.

📝 What Is Gibbs Free Energy Calculator?

The Gibbs Free Energy Calculator is an educational tool that computes the change in Gibbs free energy (ΔG) for a chemical reaction using three key inputs: enthalpy (ΔH), entropy (ΔS), and temperature (T). Gibbs free energy is a thermodynamic potential that tells you whether a reaction will occur spontaneously at constant temperature and pressure — a central question in chemistry, biochemistry, and materials science. By understanding ΔG, you can predict reaction direction, determine equilibrium constants, and optimize conditions for industrial or laboratory processes. This calculator simplifies the calculation so you can focus on analysis rather than arithmetic, making it an essential resource for students, researchers, and professionals working with chemical reactions.

🧮 Formula

ΔG = ΔH – T × ΔS

- ΔG = Gibbs free energy change (kJ/mol) — positive means non‑spontaneous, negative means spontaneous. - ΔH = Enthalpy change (kJ/mol) — heat absorbed or released during the reaction. - T = Absolute temperature (Kelvin) — must be in K, not °C. - ΔS = Entropy change (J/(mol·K)) — measure of disorder change; note that ΔS is usually given in J, so you may need to convert to kJ by dividing by 1000 when using the formula.

💡 Tips for Best Results

✨🔍 Always double‑check your units — common mistake: ΔH in kJ, ΔS in J. Convert ΔS to kJ by dividing by 1000 before calculating.

✨🌡️ Use Kelvin, not Celsius — add 273.15 to your Celsius temperature to get the correct value.

✨📊 A negative ΔG indicates an exergonic (spontaneous) reaction; a positive ΔG means an endergonic (non‑spontaneous) reaction.

✨🔄 If ΔG = 0, the reaction is at equilibrium — no net change in either direction under those conditions.

❓ Frequently Asked Questions

What does a negative Gibbs free energy mean?

A negative ΔG means the reaction is spontaneous (exergonic) at the given temperature and pressure — it will proceed without external energy input. The more negative the value, the more favorable the reaction.

Can I input temperature in Celsius?

No — the formula requires absolute temperature in Kelvin. Simply convert Celsius to Kelvin by adding 273.15 (e.g., 25 °C = 298.15 K). Our calculator expects Kelvin input for accuracy.

What if the Gibbs free energy is zero?

When ΔG = 0, the reaction is at equilibrium. There is no net change in the concentrations of reactants and products. At this point, the forward and reverse reaction rates are equal.