Enter your Calculation Method, then plug in Enthalpy Change (ΔH), Entropy Change (ΔS), and Temperature — or use an Equilibrium Constant (K) — and this Gibbs Free Energy Calculator gives you Gibbs Free Energy (ΔG), Standard Gibbs Energy (ΔG°), and tells you whether your reaction spontaneity is favorable or not.
Gibbs Free Energy (ΔG)
--
Reaction Spontaneity
--
Standard Gibbs Energy (ΔG°)
--
Gibbs free energy is calculated using ΔG = ΔH - TΔS, where ΔH is enthalpy change, T is temperature in Kelvin, and ΔS is entropy change. Alternatively, you can use ΔG° = -RT ln K for equilibrium constant calculations.
A negative ΔG indicates that the reaction is thermodynamically favorable and will occur spontaneously under the given conditions without external energy input.
At equilibrium, there is no net change in the system, meaning no driving force exists for the reaction to proceed in either direction. This state corresponds to ΔG = 0.
If ΔG < 0, the reaction is spontaneous. If ΔG > 0, the reaction is nonspontaneous and requires external energy. If ΔG = 0, the system is at equilibrium.
Enthalpy is typically expressed in kJ/mol, while entropy is in J/(mol·K). Make sure units are consistent - convert kJ to J or vice versa to match your entropy units.
Gibbs free energy tells you whether a reaction will occur spontaneously, the maximum useful work that can be extracted from the reaction, and helps predict the direction of chemical processes.
Yes, temperature can change reaction spontaneity. Since ΔG = ΔH - TΔS, increasing temperature amplifies the entropy term, which can make endothermic reactions spontaneous at high temperatures.
ΔG° is the standard Gibbs free energy change under standard conditions (298.15 K, 1 atm pressure, 1 M concentrations), while ΔG applies to any specific conditions including non-standard states.