收率（yield 或percent yield）或称作反应收率，一般用于化学及工业生产，是指在化学反应或相关的化学工业生产中，投入单位数量原料获得的实际生产的产品产量与理论计算的产品产量的比值。同样的一个化学反应在不同的气压、温度下会有不同的收率。一般而言，收率在90%以上是很高的收率，75%以上是不错的收率，60%左右是一般的收率，30%以下是很低的收率。

In chemistry, yield, also referred to as reaction yield, is the amount of product obtained in a chemical reaction. The absolute yield can be given as the weight in grams or in moles (molar yield). The percentage yield (or fractional yield or relative yield), which serves to measure the effectiveness of a synthetic procedure, is calculated by dividing the amount of the desired product obtained by the theoretical yield (the unit of measure for both must be the same):