Type a reaction and the mass of each reactant, and this free limiting reactant calculator balances the equation, finds the limiting reagent, works out the theoretical yield of your product and how much of each excess reactant is left. Add the mass you actually obtained for the percent yield.
How to find the limiting reactant
- Balance the equation.
- Convert each reactant’s mass to moles (mass ÷ molar mass).
- Divide each reactant’s moles by its coefficient. The smallest value is the limiting reactant: it runs out first.
- Use the limiting reactant and the mole ratio to find the moles, then grams, of product: the theoretical yield.
- Percent yield = actual yield ÷ theoretical yield × 100.
Percent yields under 100% are normal: reactions don’t go to completion, side reactions happen and product is lost in transfer and purification. A yield above 100% usually means the product is still wet or impure.
Frequently asked questions
What is a limiting reactant?
The reactant that is completely used up first, which stops the reaction and limits how much product can form. The others are in excess.
How do I find the limiting reactant?
Convert every reactant to moles and divide by its coefficient in the balanced equation. The smallest result is the limiting reactant. The calculator shows this ratio for each one.
What is theoretical yield?
The maximum mass of product that could form if all of the limiting reactant reacted perfectly, calculated from the mole ratio in the balanced equation.
How do I calculate percent yield?
Divide the actual mass you obtained by the theoretical yield and multiply by 100. Enter your actual yield and the calculator does it.
Related tools
Free educational tool by HawkInc. Results are calculated in your browser and rounded for display; check critical work by hand or with a second method.