Percent Yield Calculator
How much product you actually got, as a share of the most you could have got.
Worked example
You react 10.0 g of salicylic acid (C₇H₆O₃, 138.12 g/mol) to make aspirin (C₉H₈O₄, 180.16 g/mol) in a 1:1 ratio. Theoretical yield = 10.0 ÷ 138.12 × 180.16 = 13.04 g. You collect 10.8 g of dry crystals: 10.8 ÷ 13.04 × 100 = 82.8%.
Questions students ask
What is the percent yield formula?
Percent yield = (actual yield ÷ theoretical yield) × 100. Both yields must be in the same unit, grams or moles.
Can percent yield be over 100%?
Not for a pure, dry product. Results above 100% usually mean the product is still wet, contains impurities or unreacted starting material, or a weighing error was made.
Why is actual yield usually lower than theoretical?
Reactions may not go to completion (equilibrium), side reactions consume reactants, and product is lost during filtering, transferring and purification.
How do I find theoretical yield?
From the limiting reactant: moles of limiting reactant × mole ratio × molar mass of product. The stoichiometry calculator does this from the equation.