Chemistry

Instant, private, and free

Equilibrium Constant Calculator.

Calculate Kc for two explicit product and reactant species and their stoichiometric coefficients.

On-device calculationNo signup
01

Set your values

Results update as you type.

Kc: 1

Kc

1.00

How to Use

Kc = (Aproducts^ν × Bproducts^ν) ÷ (Areactants^ν × Breactants^ν). Concentrations and coefficients are visible inputs.

Use a named source for any material-specific coefficient. This page does not infer local rates, species tables, laboratory methods, or safety guidance.

Use Cases

Determine Kc for a balanced reaction

Use this calculator to find the equilibrium constant for any reaction with two products and two reactants, given their equilibrium concentrations and coefficients.

Example: For N2 + 3H2 ⇌ 2NH3, enter [NH3]=0.5, coefficient 2; [N2]=0.1, coefficient 1; [H2]=0.3, coefficient 3.

Check consistency of equilibrium data

Verify whether given concentration data and coefficients yield a plausible Kc value, useful for lab reports or textbook problems.

Example: Compare calculated Kc with literature values to validate experimental measurements.

Frequently Asked Questions

What does the Equilibrium Constant Calculator compute?
It computes the equilibrium constant Kc for a chemical reaction of the form aA + bB ⇌ cC + dD, using the molar concentrations (mol/L) and stoichiometric coefficients you enter for two products and two reactants.
How is Kc calculated from the inputs?
Kc = ([C]^c * [D]^d) / ([A]^a * [B]^b), where [C] and [D] are product concentrations, [A] and [B] are reactant concentrations, and a, b, c, d are their respective stoichiometric coefficients.
What units should I use for concentrations?
Concentrations must be entered in mol/L (molarity). The calculator uses these values directly in the Kc expression, so ensure all concentrations are in the same unit.

Tips & Common Mistakes

Tips

  • Ensure the chemical equation is balanced before entering coefficients; otherwise, Kc will be incorrect.
  • Use consistent units (mol/L) for all concentrations. If concentrations are given in other units, convert them first.
  • Double-check that you have assigned products and reactants correctly; swapping them will invert Kc.
  • For reactions with pure solids or liquids, their concentrations are constant and not included in Kc; this calculator only handles species with variable concentrations.

Common Mistakes to Avoid

  • Forgetting to raise each concentration to the power of its stoichiometric coefficient.
  • Entering coefficients as concentrations or vice versa, leading to a nonsensical Kc.
  • Using concentrations at non-equilibrium conditions; Kc is only defined at equilibrium.

Last updated: August 13, 2026