Actual yield represents the real-world amount of product you actually obtain from a chemical reaction, almost always less than the theoretical maximum. The difference between these yields tells you about reaction efficiency, purification losses, and side reactions. Percentage yield = (Actual Yield ÷ Theoretical Yield) × 100% is the standard measure of reaction efficiency.
The theoretical yield is determined by the limiting reagent—the reactant that is completely consumed first. Once it runs out, the reaction stops, regardless of how much of the other reactants remains. Calculating theoretical yield always starts with identifying this limiting factor.
