Calculator
Percent yield = (actual yield / theoretical yield) × 100. Keep actual and theoretical yields in the same unit.
Formula and assumptions
percent yield = (actual yield / theoretical yield) × 100
The result compares an observed product quantity with the theoretical product quantity calculated from stoichiometry. Use the same unit for both yields.
Assumption: Actual and theoretical yields use the same unit and refer to the same product.
Variables and units
Worked example
An actual yield of 8 g from a theoretical yield of 10 g is 80%.
Why yields fall short of 100%
A reaction with a theoretical yield of 12.5 g gives 10.2 g of dry product: percent yield = 10.2 / 12.5 × 100 = 81.6%. Losses come from incomplete reactions, side reactions, transfers between vessels and product left in solution during recrystallisation.
A yield above 100% almost always means the product is not pure or not dry: trapped solvent or water adds mass. Always calculate the theoretical yield from the limiting reagent, not from whichever reactant is easiest to weigh.
Important limits
The tool does not determine theoretical yield from a chemical equation.
Reference and related tools
OpenStax: Reaction stoichiometry. Return to Chemistry Calculators for the other tools in this group.