Limiting Reagent Calculator

Identify the limiting reagent and excess reagent for a two-reactant reaction.

How It Works

Enter the moles of two reactants and their stoichiometric coefficients. The calculator determines which reagent is completely consumed first (limiting) and how much of the other remains (excess).

Formula

Limiting reagent = reactant that produces fewer moles of product

Examples

3 mol H2 + 2 mol N2 (ratio 3:1 for NH3): H2 is limiting → produces 2 mol NH3 | 4 mol Fe + 3 mol O2 → Fe2O3: check which runs out first

Frequently Asked Questions

What is the limiting reagent?

The limiting reagent is the reactant that is completely consumed in a chemical reaction, determining the maximum amount of product that can form.

How do I identify the limiting reagent?

Divide the moles of each reactant by its stoichiometric coefficient. The reactant with the smallest result is the limiting reagent.

What is the excess reagent?

The excess reagent is the reactant that remains after the limiting reagent is consumed. Its leftover amount is called the excess.