Equilibrium Constant Calculator
Calculate the equilibrium constant from equilibrium concentrations.
About Equilibrium Constant Calculator
Concentrations are raised to their stoichiometric coefficients, which is why K is so sensitive to coefficients. A K above one means products dominate at equilibrium, and the free energy change follows directly. K is temperature dependent but concentration independent, which is what makes it a genuine constant rather than a measured ratio.
Formula
Equilibrium Constant
K = [products]^coefficients ÷ [reactants]^coefficients; ΔG° = −RT ln K
- K
- Equilibrium constant, dimensionless by convention
- ΔG°
- Standard free energy change, negative when products are favoured
Worked example
With the default values below, Equilibrium Constant Calculator returns Equilibrium Constant of 8.00000000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Product A concentrationminimum 0 mol/L
- 0.4 mol/L
- Coefficient of product Aaccepts 1–10
- 2
- Reactant B concentrationminimum 0 mol/L
- 0.1 mol/L
- Coefficient of reactant Baccepts 1–10
- 1
- Reactant C concentrationminimum 0 mol/L
- 0.2 mol/L
Results
- Equilibrium Constant
- 8.00000000
- Logarithm of the Constant
- 0.90309
- Position of Equilibrium
- Favours products
- Standard Gibbs Free Energy Change
- -5.1548 kJ/mol
- Product Term
- 0.16000000
Step by step
- 1Values used
- 2Equilibrium Constant
- 3Equilibrium Constant= 8.00000000
- 4Logarithm of the Constant= 0.90309
- 5Position of Equilibrium= Favours products
- 6Standard Gibbs Free Energy Change= -5.1548 kJ/mol
- 7Product Term= 0.16000000
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 8 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Equilibrium Constant calculated?
K = [products]^coefficients ÷ [reactants]^coefficients; ΔG° = −RT ln K Concentrations are raised to their stoichiometric coefficients, which is why K is so sensitive to coefficients. A K above one means products dominate at equilibrium, and the free energy change follows directly.
Why does Equilibrium Constant matter?
K is temperature dependent but concentration independent, which is what makes it a genuine constant rather than a measured ratio.
What values do I need to enter?
This calculator takes 5 inputs: Product A concentration, Coefficient of product A, Reactant B concentration, Coefficient of reactant B, Reactant C concentration. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.