Percent Yield Calculator

How it is calculated

Percent yield tells you how much of the product you expected to make was actually collected: percent yield = actual yield / theoretical yield × 100. The theoretical yield is the maximum amount the balanced chemical equation allows, worked out from the limiting reactant. The actual yield is what you measured after the reaction, for example in grams. Both must be in the same unit. The tool also shows the amount lost, theoretical − actual, in that unit. The theoretical yield must be greater than zero and the actual yield cannot be negative. A value above 100% is not blocked, but it usually points to a wet or impure product or a calculation error, not to a reaction that makes extra mass.

Common mistakes

• Using the mass of the starting material as the theoretical yield instead of calculating it from the balanced equation and the limiting reactant.
• Mixing units, such as actual yield in milligrams and theoretical in grams.
• Weighing the product while it is still wet or has leftover solvent, giving a yield above 100%.
• Swapping the two values, which turns a 78% yield into 128%.
• Computing the theoretical yield from the reactant in excess rather than the limiting one.