Percent yield in chemistry
Percent yield compares the amount of product actually obtained with the maximum amount predicted from reaction stoichiometry. It is a measure of experimental recovery, not the same concept as atom economy.
Actual and theoretical yield must describe the same product and use compatible units. Masses, molar amounts, or another appropriate property can be compared when both values use the same basis.
How to use the percent yield calculator
- Choose the unknown: Select percent, actual, or theoretical yield.
- Enter known values: Use the same product and compatible units for both yield quantities.
- Calculate: Generate the missing yield value from the entered quantities.
- Interpret: Check unusually high results for wet product, impurities, or inconsistent units.
Formula and variables
Divide the recovered amount by the stoichiometrically predicted amount, then multiply by 100.
Percent yield = (actual yield / theoretical yield) × 100%- Y% — Percent yield
- Actual yield expressed as a percentage of theoretical yield (%)
- Yactual — Actual yield
- Measured amount of isolated product (any consistent quantity unit)
- Ytheoretical — Theoretical yield
- Maximum product predicted by stoichiometry (same unit as actual yield)
Percent yield from product mass
A reaction produces 21.5 g when its theoretical yield is 25.0 g.
- Actual yield
- 21.5 g
- Theoretical yield
- 25.0 g
- Percent yield = (21.5 / 25.0) × 100%
- Percent yield = 86.0%
Result: The percent yield is 86.0%.
The experiment recovered 86% of the stoichiometrically predicted product.
Understanding your results
What the result means
A result below 100% commonly reflects incomplete reaction, competing reactions, or product lost during isolation and purification.
- A result above 100% often signals retained solvent, contamination, or a measurement or unit error.
- Percent yield alone does not identify why material was lost.
Assumptions
- Actual and theoretical values refer to the same chemical product.
- Both yields use compatible units and the same quantity basis.
- The theoretical yield is based on the limiting reactant and a balanced equation.
Limitations
- Does not balance reactions or calculate theoretical yield from reactant amounts.
- Does not account for purity, moisture, solvent retention, or analytical uncertainty.
- A calculated percentage does not diagnose reaction mechanism or process losses.
Common mistakes
- Dividing theoretical yield by actual yield.
- Comparing grams with moles without conversion.
- Using the amount of reactant instead of the amount of product.
- Treating crude or wet product mass as pure isolated product.
Practical use cases
Reaction-yield homework
Check the final yield step after theoretical yield has been established.
Laboratory reports
Report recovered product relative to the predicted maximum.
Frequently asked questions
Can percent yield be greater than 100%?
The arithmetic can exceed 100%, but the result usually indicates impurities, retained solvent, incomplete drying, or inconsistent measurements.
Do actual and theoretical yield have to be in grams?
No. They may use moles, mass, or another appropriate property as long as both refer to the same product and use compatible units.
Is percent yield the same as atom economy?
No. Percent yield describes experimental recovery; atom economy describes how reactant atoms are incorporated into the desired product by the reaction equation.
Sources and review
- Reaction Yields — OpenStax Chemistry 2e. Accessed 2026-07-13.
Reviewed 2026-07-13.