About the Equilibrium Constant Calculator

The equilibrium constant is the ratio of product concentration terms to reactant concentration terms, each raised to its stoichiometric coefficient. For the default 2A + B ⇌ 2C + D with concentrations 0.5/0.3/0.8/0.6 M: Kc = 0.8² × 0.6 ÷ (0.5 × 0.3) = 2.56 — products mildly favored.

Kc vs Q

The same expression computed before equilibrium is the reaction quotient Q. Comparing Q to Kc predicts the shift: Q < Kc drives forward, Q > Kc drives reverse, Q = Kc means equilibrium. Because Kc depends only on temperature, it lets you predict direction from any mixture.