Percent Yield Calculator
Calculate the percent yield of a chemical reaction — how efficient your synthesis was — by comparing actual to theoretical yield.
How to use this percent yield calculator
- 1Calculate theoretical yield from stoichiometry: moles of limiting reagent × molar ratio × molar mass of product.
- 2Weigh your actual collected product.
- 3Enter both — units must match (both grams, both moles, etc.).
- 4A result above 100% indicates impurities or measurement error.
How it's calculated
Percent yield = (actual yield ÷ theoretical yield) × 100%. Theoretical yield is the stoichiometric maximum from the limiting reagent.
About the Percent Yield Calculator
Percent yield measures reaction efficiency. Even a 90% yield means 10% of starting material was lost to side reactions, incomplete conversion, or product lost during purification.
Industrial chemists obsess over yield — even 1% improvement in a million-kg/year process saves enormous costs. Green chemistry encourages maximising both yield and atom economy (the fraction of starting material atoms incorporated into the final product).
Frequently asked questions
Can percent yield exceed 100%?
In theory, no. Above 100% means the product contains impurities (trapped water, side products) or there's a weighing error.
What is a good percent yield?
Teaching labs: 70–90% is good. Industrial processes: 95%+. Complex organic syntheses: 40–60% may be considered acceptable.
What is theoretical yield?
The maximum amount of product possible if the limiting reagent reacted completely with 100% efficiency, calculated from stoichiometry.