Percent Yield Calculator
Enter the actual yield and the theoretical yield, or work the theoretical yield out from the mass of the limiting reactant.
Worked examples
Known theoretical yield
Actual 15 g, theoretical 20 g
75%
15 / 20 x 100.
From the reactant
10 g of a reactant of 40 g/mol making a 100 g/mol product 1 to 1, 20 g collected
Theoretical 25 g, yield 80%
10 / 40 x 100 = 25 g.
About Percent Yield Calculator
The theoretical yield is the most product a reaction could make if every bit of the limiting reactant turned into it. In practice some is lost to side reactions, incomplete reaction and transfer losses, so the actual yield is smaller. The percent yield is the actual yield divided by the theoretical yield, multiplied by 100. It is a measure of how well the experiment went.
To find the theoretical yield, convert the mass of the limiting reactant to moles, multiply by the mole ratio from the balanced equation, and convert back to a mass using the molar mass of the product. This calculator can do all of that, or you can type the theoretical yield if you already have it. A yield above 100% usually means the product is still wet or impure, and the page points that out.
How to use Percent Yield Calculator
- Choose whether you know the theoretical yield or want it worked out.
- Enter the actual yield you collected, in grams.
- For a calculation, enter the mass and molar mass of the limiting reactant, the molar mass of the product and the mole ratio.
- Read the percent yield and the theoretical yield.
Common uses
- Lab reports on synthesis experiments
- Judging the efficiency of a reaction step
- Planning how much reactant is needed for a target mass of product
- Chemistry exam practice
Frequently asked questions
What is the percent yield formula?
Percent yield = actual yield / theoretical yield x 100%. An actual yield of 15 grams from a theoretical 20 grams is 75%.
How do I find the theoretical yield?
Convert the limiting reactant to moles, use the balanced equation's mole ratio to find the moles of product, and multiply by the product's molar mass.
What is the limiting reactant?
It is the reactant that runs out first and so controls how much product can form. Always work from it, not from the reactant in excess.
Can the yield be over 100%?
Not in theory. A figure above 100% usually points to an impure or wet product, or to a weighing or calculation mistake.