Limiting Reagent Calculator with Steps
Use this free limiting reagent calculator to identify the limiting reactant, excess reactant, and maximum amount of product formed using mole ratios from a balanced chemical equation.
Calculate Limiting Reagent
Enter the amount and coefficient for two reactants and one product. This calculator assumes all amounts are in moles.
What is a Limiting Reagent?
The limiting reagent is the reactant that runs out first in a chemical reaction. Once the limiting reagent is used up, the reaction stops, even if another reactant is still available.
The reactant that produces the smaller amount of product is the limiting reagent.
Worked Example
For the equation 2H₂ + O₂ → 2H₂O, suppose we have 4 mol H₂ and 1 mol O₂.
From O₂: 1 × 2 ÷ 1 = 2 mol H₂O
O₂ produces less product, so O₂ is the limiting reagent.
Practice Question
For 2H₂ + O₂ → 2H₂O, if you have 6 mol H₂ and 2 mol O₂, which reactant is limiting?