Percent Yield Calculator
Calculate percent yield from actual and theoretical masses, or find either mass from a known percentage yield. Mass inputs can use milligrams, grams or kilograms.
- Actual yield
- 8.5 g
- Theoretical yield
- 10 g
- Percent yield
- 85%
Theoretical yield must be supplied or calculated separately from reaction stoichiometry.
Show working
Convert both masses to the same unit (grams). Percent yield = actual / theoretical x 100 8.5 g / 10 g x 100 = 85%
Percent yield formula
Percent yield compares the amount of product actually obtained with the amount theoretically expected. It expresses actual yield as a percentage of theoretical yield.
Percent yield = actual yield / theoretical yield x 100
If an experiment produces 8.5 g and the theoretical yield is 10 g, the percent yield is 8.5 / 10 x 100 = 85%. Actual yield is the amount measured after the experiment; theoretical yield depends on the reaction and available reactants.
For the chemical meaning of these quantities, see OpenStax Chemistry 2e: Reaction Yields. This calculator handles the percentage relationship once the relevant values are known.
Keep the units consistent
The two masses must describe the same substance and use compatible units. This tool converts milligrams, grams and kilograms to grams before calculating the ratio.
For example, actual yield of 850 mg equals 0.85 g. Compared with a theoretical yield of 1 g, this gives 85%. Dividing 850 by 1 without converting units would produce an incorrect answer.
Converting between mass and moles requires the substance’s molar mass, so grams and moles cannot be treated as interchangeable. This page accepts mass units only.
Find actual or theoretical yield
| Unknown | Formula | Example |
|---|---|---|
| Actual yield | Theoretical yield x percent yield / 100 | 20 g x 75 / 100 = 15 g |
| Theoretical yield | Actual yield / (percent yield / 100) | 12 g / 0.80 = 15 g |
Finding a theoretical mass from a known actual mass and percentage is an algebraic rearrangement. It is not the same as predicting theoretical yield from reactant quantities, a balanced equation and the limiting reagent. Those chemical calculations must be completed separately.
Why might a measured yield exceed 100%?
The formula can return more than 100% when the measured actual mass exceeds the theoretical mass. For example, 11 g compared with 10 g gives 110%. In an experiment, check for retained solvent, contamination, incomplete drying, measurement error or an incorrect theoretical calculation.
The calculator flags this situation instead of changing the result to 100%. A mathematically computed ratio does not confirm the purity of a sample or the validity of the experiment.
Yield is also different from percent error. Yield divides actual output by theoretical output; percent error compares the difference with a reference value. For comparing two measurements without a designated reference, see percentage difference.
Common questions
Can percent yield be zero?
Yes. Zero actual product and a positive theoretical yield give 0%. But a zero theoretical yield makes the percent-yield formula undefined, and a 0% yield cannot uniquely determine theoretical yield by reverse division.
What is a good percent yield?
It depends on the reaction, process and purity requirements. There is no universal target that applies to every experiment. Compare against the method and conditions relevant to your work.
Is percent recovery the same as percent yield?
No. Recovery commonly compares the amount recovered with the amount initially present. Reaction yield compares product obtained with theoretical product. The arithmetic can look similar while the denominator represents something different.
Related calculators
Back to the Percent Calculator.