Limiting Reactant Calculator
Finds the reactant that runs out first in a balanced equation. Enter the coefficients from the balanced equation.
Limiting reactant
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Theoretical yield of product —
Excess reactant left over —
Reactant by reactant
Reading this —
The formula
compare moles ÷ coefficient for each reactant product = smallest value × product coefficient × molar mass
Dividing by the coefficient puts both reactants on the same scale.
What to watch out for
The default values are hydrogen and oxygen forming water: 2H₂ + O₂ → 2H₂O.
Frequently Asked Questions
How do I find the limiting reactant?
Convert each mass to moles, divide by its coefficient, and pick the smallest result.
Does the smaller mass always run out first?
No. In the default values, 4 g of hydrogen is far less mass than 16 g of oxygen, yet oxygen limits: 0.5 against 0.9921 for hydrogen.