Percent Yield Calculator

Percent yield measures how much product you actually obtained from a chemical reaction compared with the maximum amount that stoichiometry predicts you could obtain. It is expressed as a percentage and calculated as actual yield divided by theoretical yield, multiplied by 100. The actual yield is the mass of product you recovered and measured in the lab; the theoretical yield is the mass you would obtain if every mole of limiting reagent were converted perfectly to product with no losses. In practice, yields are always below 100 percent because some product is lost during transfer, filtration or evaporation, side reactions consume some starting material, or the reaction does not go to completion. Understanding percent yield helps you evaluate how efficiently a reaction was carried out, compare different synthetic routes, and estimate the cost of producing a target amount of material. This calculator lets you enter the actual and theoretical yields in any consistent mass unit, grams being the most common, and returns the percent yield, the mass shortfall (the amount of product not recovered), and an efficiency description. You can also reverse the calculation to find the theoretical yield from a known percent yield and actual yield, or find the actual yield from percent yield and theoretical yield. The tool is used in teaching labs at secondary and university level, and in industrial process evaluation.

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Both yields must be in the same mass unit. If your yield exceeds 100%, the product may contain moisture or impurities and should be dried before re-weighing.