Limiting Reagent Calculator
Fewest equivalents, not fewest moles.
Work out Limiting Reagent. Fewest equivalents, not fewest moles. Says where the approximation breaks.
Limiting reagent
H2
0.6667 mol of product · 11.354 g
The limiting reagent is not the one present in the smallest amount — it is the one with the fewest equivalents, meaning moles divided by its coefficient. With equal moles of nitrogen and hydrogen, hydrogen limits, because the equation needs three of it per nitrogen. Comparing masses, or even moles, gets this wrong exactly when it matters.
How the Limiting Reagent Calculator works
The limiting reagent is the one with the fewest equivalents — moles divided by its stoichiometric coefficient — not the one present in the smallest amount. With equal moles of nitrogen and hydrogen, hydrogen limits, because the equation needs three of it per nitrogen.
Also known as: limiting reactant calculator · excess reagent calculator · theoretical yield from limiting reagent · how to find the limiting reactant
Frequently asked questions
How do I find the limiting reagent?
Divide each reagent's moles by its coefficient in the balanced equation. The smallest result limits the reaction. Comparing masses, or even moles, gets this wrong exactly when it matters.
How do I calculate theoretical yield?
Multiply the limiting reagent's equivalents by the product's coefficient, then by the product's molar mass. That is the maximum obtainable if everything reacted perfectly.
How much excess reagent is left?
The difference between each reagent's equivalents and the limiting one's, multiplied back by its coefficient. This page reports it per reagent.
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