Equilibrium Concentration Calculator

About this calculator

For a simple reversible reaction A ⇌ B starting with only reactant A present, the equilibrium constant Keq = [B]/[A] tells you the ratio the concentrations settle into once the forward and reverse reaction rates become equal — a large Keq means the reaction favors product B at equilibrium, while a small Keq means most of the material stays as A.

Given the initial concentration of A and Keq, an ICE table (Initial, Change, Equilibrium) approach lets you solve directly for both equilibrium concentrations: [B] = Keq/(1+Keq) times the initial concentration, and [A] is what remains. This is a foundational calculation in general chemistry for reactions simple enough to have a 1:1 stoichiometry and no other competing species.