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Percent Yield Calculator

Find the percent yield of a chemical reaction.

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.

Worked example

The balanced equation predicts a theoretical yield of 10.5 g, and you collect 8.2 g of dry product. Divide: 8.2 / 10.5 = 0.7810. Multiply by 100: the percent yield is 78.10%. The amount not recovered is 10.5 − 8.2 = 2.30 g. This loss can come from an incomplete reaction, side reactions, or product left on glassware and filter paper.

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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.

About this calculator

This calculator computes reaction percent yield: % yield = (actual yield / theoretical yield) × 100, comparing what was actually produced in the lab against the maximum predicted by stoichiometry from the limiting reagent.

Chemistry students, lab technicians, and process chemists use it to evaluate how efficient a reaction or synthesis was, and to flag losses from side reactions, incomplete reactions, or purification steps.

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Comments (1)

  • Editorial team

    The tool does not stop at 100 percent, so a result above it and a negative lost amount are shown as they are. In a real lab that is a flag, not a success: the usual suspects are product that is still wet with solvent, impurities, or a wrong theoretical yield from picking the wrong limiting reagent. Recheck those before trusting the number. Which reaction are you running, and where do you tend to lose product?

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