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Gibbs Free Energy Calculator (ΔG = ΔH - TΔS)

Calculate Gibbs free energy change (ΔG) to determine the thermodynamic spontaneity of chemical reactions.

Input Parameters

Instant Real-time Calculation

Enthalpy Change (ΔH in kJ/mol)

Absolute Temperature (Kelvin)

Entropy Change (ΔS in J/(mol·K))

Result Chemistry

Gibbs Free Energy (ΔG)

-- kJ/mol

Export calculation:

Calculation Logic:

Thermodynamic criterion for spontaneity at constant temperature and pressure. When ΔG < 0, the forward reaction is spontaneous (exergonic). When ΔG > 0, it is non-spontaneous (endergonic).

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Understanding Gibbs Free Energy Calculator (ΔG = ΔH - TΔS) & Formula

Mathematical Formula: ΔG = ΔH - (T × ΔS); (ΔG < 0 is exergonic & spontaneous)

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Spontaneity Four-Quadrant Rules

ΔH Sign	ΔS Sign	ΔG Sign	Spontaneity Condition
Negative (Exothermic)	Positive (Disorder increases)	Always Negative (< 0)	Spontaneous at ALL temperatures
Negative (Exothermic)	Negative (Disorder decreases)	Negative at low T	Spontaneous ONLY at low temperatures
Positive (Endothermic)	Positive (Disorder increases)	Negative at high T	Spontaneous ONLY at high temperatures
Positive (Endothermic)	Negative (Disorder decreases)	Always Positive (> 0)	Non-spontaneous at ALL temperatures

How to Use the Gibbs Free Energy Calculator (ΔG = ΔH - TΔS)

1 Input enthalpy change ΔH in kJ/mol.
2 Input temperature in Kelvin.
3 Input entropy change ΔS in J/(mol·K) (note: auto-converted to kJ).
4 Obtain ΔG and check if the reaction is spontaneous.

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