Percent Yield Calculator
Enter the amount you actually obtained and the maximum amount predicted by stoichiometry to get the percent yield of your reaction.
Actual over theoretical
Enter the actual yield and the theoretical yield and the calculator returns the percent yield — how much of the maximum possible product you recovered.
Same unit for both
Keep both yields in the same unit — grams and grams, or moles and moles — so the units cancel and the result is a clean percentage.
What is percent yield?
How efficient your reaction was
The percent yield calculator tells you how efficiently a chemical reaction produced its product. Percent yield compares the amount you actually obtained — the actual yield — with the maximum amount the reaction could ever make, the theoretical yield predicted by stoichiometry. It is expressed as a percentage, so a value of 85% means you recovered 85% of the most the reaction could possibly give. Chemists use it to judge how well a synthesis worked, to compare different reaction conditions, and to spot losses or contamination when a number comes out unexpectedly high or low.
Enter your actual yield and the theoretical yield in the same unit to get the percent yield of your reaction instantly.
Percent yield is the actual yield divided by the theoretical yield, multiplied by 100 to turn the ratio into a percentage.
percent yield = (actual ÷ theoretical) × 100Because percent yield is a ratio, the units of the two yields cancel, so the answer is always a pure percentage. Keep both numbers in the same unit — grams and grams, or moles and moles — and the result comes back as a percentage you can compare directly across reactions.
Suppose a reaction could theoretically produce 10 g of product, and you isolate 8.5 g in the lab.
Divide actual by theoretical
8.5 ÷ 10 = 0.85 — the fraction of the maximum you recovered.
Multiply by 100
0.85 × 100 = 85 — convert the fraction to a percentage.
Read the result
The percent yield is 85%, a strong result for many syntheses.
A result above 100% is physically impossible: it usually means the product is still wet, contains impurities, or the theoretical yield was miscalculated — a cue to re-check your work rather than a genuine surplus.
The formula is exact, but a couple of practical points are worth keeping in mind.
Consistent units and a correct theoretical yield
Percent yield is only as reliable as the two numbers you feed it. Keep both yields in the same unit so they cancel, and make sure the theoretical yield is worked out from the limiting reactant using correct stoichiometry — an overstated theoretical yield deflates the percentage and an understated one can push it past 100%. Values above 100% point to impurities, residual solvent, or a calculation error, not extra product.