Limiting Reagent & Percent Yield Calculator
Reaction
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Finding the limiting reagent — the method
- Balance the equation to get the mole ratios.
- Convert each reactant to moles (grams ÷ molar mass, or use the moles directly).
- Divide each by its coefficient. The smallest result is the limiting reagent — it runs out first.
- Theoretical yield: use the limiting reagent's moles and the mole ratio to find moles of product, then × molar mass for grams.
- Percent yield: (actual ÷ theoretical) × 100. Whatever isn't the limiting reagent is left over in excess.
This tool balances with chempy and uses exact molar masses, then shows the limiting reagent, the excess left over, the theoretical yield, and the percent yield.
Frequently asked
Convert each reactant to moles, divide by its coefficient in the balanced equation, and the smallest value is the limiting reagent — it caps the product. The rest are in excess.
From the limiting reagent's moles, apply the mole ratio to get moles of product, then multiply by the product's molar mass for grams.
Percent yield = (actual yield ÷ theoretical yield) × 100. Below 100% is normal due to losses and side reactions.
Yes — write the unit, e.g.
N2: 0.5 mol or H2: 3 g.Yes — free, no signup, balanced and computed with the open-source chempy library.