Limiting Reactant Calculator
For a reaction with two reactants A and B in ratio a:b, find which one runs out first.
Result
Limiting reactant
B
Reaction extent: 1.6667 (in moles of "1 unit of reaction").
- A : eq (moles/coef)2 / 1 = 2.0000
- B : eq (moles/coef)5 / 3 = 1.6667
- A consumed1.6667 mol
- B consumed5.0000 mol
- A leftover (excess)0.3333 mol
- B leftover (excess)0.0000 mol
Step-by-step
- For each reactant, divide moles by stoichiometric coefficient.
- A/1 = 2.0000; B/3 = 1.6667.
- Smaller value is the limiting reactant: B.
How to use this calculator
- Enter moles of A and B.
- Enter their coefficients from the balanced equation.
- Read which is limiting and how much of each is consumed/leftover.
About this calculator
In any chemical reaction with multiple reactants, one will run out first — the limiting reactant. To find it, divide each reactant's moles by its stoichiometric coefficient. Whichever ratio is smallest is limiting; the others are in excess. The reaction yield is determined entirely by the limiting reactant.
Frequently asked
Same approach: find moles/coefficient for each, smallest wins. The calculator handles 2; for more, do the math by hand.
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