Limiting Reagent Calculator

Calculate limiting reactants, theoretical yields, and excess reactants for chemical reactions. Perfect for stoichiometry, reaction planning, and yield optimization.

Limiting Reagent Calculator

Reactants

Products

About Limiting Reagents

Key Concepts

  • Limiting Reagent: Reactant that is completely consumed first
  • Theoretical Yield: Maximum amount of product possible
  • Excess Reactant: Reactant left over after reaction
  • Stoichiometric Ratio: Molar ratio from balanced equation
  • Percent Yield: Actual yield / theoretical yield × 100%

How to Find Limiting Reagent

  1. Write the balanced chemical equation
  2. Convert all amounts to moles
  3. Divide moles by coefficient for each reactant
  4. Smallest ratio identifies the limiting reagent
  5. Use limiting reagent to calculate theoretical yields

Example Reaction

H₂ + O₂ → 2H₂O

If you have 2.0 mol H₂ and 1.0 mol O₂, H₂ is limiting (ratio: 2.0/1 = 2.0 vs 1.0/1 = 1.0)

Common Molecular Weights

H2O18.02 g/mol
CO244.01 g/mol
H22.02 g/mol
O232 g/mol
N228.02 g/mol
HCl36.46 g/mol
H2SO498.08 g/mol
NaOH40 g/mol
NaCl58.44 g/mol
CaCO3100.09 g/mol
Fe2O3159.69 g/mol
Al2O3101.96 g/mol
CH416.04 g/mol
C2H5OH46.07 g/mol
C6H12O6180.16 g/mol

How to Use

  1. Enter the chemical formulas for reactants and products
  2. Specify stoichiometric coefficients from balanced equation
  3. Input available moles and molecular weights
  4. Click Calculate to find limiting reagent and yields
  5. Optionally enter actual yield for percent yield

Common Applications

  • Chemical synthesis planning
  • Reaction optimization
  • Cost analysis of reactions
  • Laboratory procedure design
  • Industrial process optimization

Important Notes

  • Always use balanced chemical equations
  • Molecular weights must be accurate
  • Moles must be in the same units
  • Excess reactants are not wasted in calculations
  • Percent yield cannot exceed 100%