Percent Yield Calculator
Enter the actual yield you obtained and the theoretical yield you expected to find the percent yield of your reaction.
Percent yield measures how efficient a reaction was: the actual yield divided by the theoretical yield, times 100. If a reaction should have produced 10 grams of product (theoretical) but you recovered 8 grams (actual), the percent yield is 8 ÷ 10 × 100 = 80%. A yield above 100% signals impurities or leftover solvent in the product.
How to Use This Calculator
Enter two numbers: the actual yield (how much product you really obtained) and the theoretical yield (the maximum the reaction could produce according to stoichiometry). Both must be in the same unit — grams and grams, or moles and moles. The calculator returns the percent yield, a measure of how efficiently the reaction converted reactants into the product you wanted.
The actual yield comes from weighing your purified product. The theoretical yield comes from a stoichiometry calculation: find the limiting reactant, convert to moles of product, then to grams. Once you have both, this tool does the final division.
How the Calculation Works
Percent yield is simply the fraction of the maximum possible product you actually got, expressed as a percentage: (actual ÷ theoretical) × 100. The theoretical yield assumes the reaction goes to completion with no losses and the limiting reactant is fully converted — the ideal case. The actual yield is always equal to or (in practice) less than the theoretical yield, because of incomplete reactions, side reactions, and product lost during transfer, filtration and purification.
Worked Example
A synthesis has a theoretical yield of 10.0 g of product. After running the reaction and purifying, you weigh 8.0 g of dry product. Percent yield = (8.0 ÷ 10.0) × 100 = 80%. That is a solid result for many organic reactions. If you had recovered only 6.5 g, the yield would be 65%; if a competing side reaction and messy workup left just 4.0 g, it would be 40%.
What the Result Means
A higher percent yield means a more efficient reaction and workup. Yields near 100% are common for clean, simple reactions; multistep organic syntheses often accept 50–90% per step, and the overall yield is the product of each step's yield. A yield above 100% is physically impossible and always means an error — usually the product is not fully dry, still contains solvent, or is contaminated with an impurity, so it weighs more than pure product should. Dry and reweigh, or re-purify, and recalculate.
Assumptions and Limitations
The calculation is exact arithmetic, so its accuracy depends entirely on your two inputs. The theoretical yield must be computed correctly from the limiting reactant — a mistake there throws off the percentage. Actual and theoretical yields must use the same unit. Percent yield rates efficiency, not purity: a reaction can give a high yield of impure product, or a low yield of very pure product, so yield and purity are reported separately.
Who Uses a Percent Yield Calculator
Chemistry students use this to rate a reaction's efficiency by comparing actual to theoretical yield. Run it for lab reports and stoichiometry homework, or to judge how well a synthesis went. Enter the actual and theoretical yields to get the percent yield.
Related Calculators
Molarity Calculator
Find molar concentration from mass, molar mass and solution volume.
Open calculator →Dilution Calculator
Find how much stock solution to use with the C1V1 = C2V2 equation.
Open calculator →Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, moles or temperature.
Open calculator →Molar Mass Calculator
Type a chemical formula to get its molar mass in g/mol.
Open calculator →Frequently Asked Questions
How do I calculate percent yield?
Divide the actual yield by the theoretical yield and multiply by 100. For example, 8 g actual ÷ 10 g theoretical × 100 = 80% yield.
What is theoretical yield?
It is the maximum amount of product a reaction can make, calculated from the limiting reactant assuming the reaction goes to completion with no losses. It is the denominator in the percent yield formula.
Can percent yield be over 100%?
Not truly. A value above 100% means the measured product is impure or not fully dry — it contains extra mass from solvent or contaminants. Dry and re-weigh the product, then recalculate.
What is a good percent yield?
It depends on the reaction. Simple reactions can approach 100%, while multistep organic syntheses often consider 70–90% per step good. Overall yield is the product of all the individual step yields.
Why is actual yield less than theoretical?
Because of incomplete reactions, competing side reactions, and product lost during transfers, filtration, washing and purification. Some loss is almost unavoidable in practice.
Do actual and theoretical yield need the same units?
Yes. Use grams for both or moles for both. Mixing units gives a meaningless percentage. Most often both are in grams.
Looking for a different calculator?
CalculatorPlus has free tools across finance, construction, math, health and more — each one showing the formula and a worked example.