Reaction Yield Calculator

Enter reactant and product information to find theoretical and percent yield.

Reactant mass (g)

Reactant molar mass (g/mol)

Product molar mass (g/mol)

Mole ratio (product:reactant)

Actual yield (g) — if known

Moles of reactant —

Moles of product (theoretical) —

Theoretical yield —

Percent yield —

Theoretical yield = (reactant mass / reactant MM) × ratio × product MM. Percent yield = (actual / theoretical) × 100%.

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How to Calculate Reaction Yield

Theoretical yield is the maximum amount of product that could be formed from a given amount of reactant, assuming 100% conversion. It is calculated from stoichiometry.

Percent yield compares actual yield to theoretical yield: % yield = (actual / theoretical) × 100. Yields above 100% indicate impurities or measurement error. Typical lab yields range from 40–90% depending on the reaction.

Percent yield = (actual yield / theoretical yield) × 100. Theoretical yield is what stoichiometry predicts from the limiting reagent; actual yield is what you isolated from the reaction. A 78% yield means 22% of the theoretical product was lost to side reactions, incomplete reaction, or purification losses.

Example: theoretical yield of aspirin from 5.0g of salicylic acid (MW 138.12 g/mol) in an esterification reaction: 5.0/138.12 = 0.0362 mol salicylic acid → 0.0362 mol aspirin × 180.16 g/mol = 6.52g theoretical yield. If you actually isolate 5.08g: percent yield = 5.08/6.52 × 100 = 77.9%.

Atom economy = (mass of desired product / total mass of all products) × 100. A reaction producing 180g of desired product and 36g of water byproduct has atom economy = 180/(180+36) × 100 = 83.3%. High atom economy is a principle of green chemistry — reactions that incorporate most of their reactant atoms into the desired product generate less waste.

Typical percent yields in organic synthesis: simple esterifications 60–85%, Grignard reactions 70–90%, recrystallizations 50–70% (intentionally sacrificing yield for purity), biochemical extractions 10–50% depending on purification cascade. Multi-step syntheses multiply yields: 5 steps at 80% each gives 0.8⁵ = 32.8% overall yield.