Percent Yield Calculator

Percent yield measures how much product a chemical process actually produced compared with the maximum amount predicted by stoichiometry. The theoretical yield is calculated from the balanced reaction and the limiting reactant. The actual yield is the isolated, measured amount obtained after reaction, workup, purification, and drying. Dividing actual yield by theoretical yield and multiplying by 100 gives the percent yield. A result of 100 percent means the measured amount exactly matches the stoichiometric maximum. Results below 100 percent are common because reactions may not reach completion, competing reactions may consume material, transfers can lose product, and purification may discard some desired compound. A low yield can also reflect inaccurate reagent quantities, unsuitable temperature or time, decomposition, or incomplete isolation. Percent yield therefore summarizes the entire practical process rather than only the reaction mechanism. Both yields must describe the same product and use compatible units. Grams divided by grams or moles divided by moles produce the same percentage when each value refers to the same pure substance. Do not compare product mass directly with reactant mass. First use the balanced equation, reactant amounts, and molar masses to find the theoretical amount of product. When several reactants are present, calculate the product possible from each and use the smallest amount, which identifies the limiting reactant. Percent yields greater than 100 usually indicate that the isolated material contains solvent, water, salts, unreacted starting material, or another impurity. They can also arise from weighing, transcription, stoichiometry, or unit errors. A value above 100 does not prove unusually efficient chemistry because conservation of matter prevents obtaining more pure product than the theoretical maximum. Dry or purify the sample as appropriate and review the theoretical-yield calculation before reporting the value. Percent yield should be interpreted alongside purity, selectivity, reproducibility, and scale. A high crude yield may include impurities, while a lower isolated yield can represent highly pure material. For process comparison, use consistent isolation and analytical methods and report uncertainty or replicate variation. This calculator performs the final ratio only; it does not balance reactions, identify the limiting reagent, or verify product identity. Those steps must be completed before the theoretical and actual values are entered.