Percent Yield Calculator
Find the percent yield of a chemical reaction from actual and theoretical yield, reverse-solve either value, or average several trials. Works with grams and moles.
— percent yield
— g actual yield
— g theoretical yield
Enter each trial in the same unit (all grams or all moles — the ratio cancels out).
| Trial | Actual yield | Theoretical yield | % yield |
|---|
Worked examples
Example 1 — Percent yield
You isolated 43.89 g of product; the equation predicts 52.0 g.
(43.89 / 52.0) x 100 = 84.40%.
Example 2 — Find actual yield
A reaction runs at 84.40% yield with a theoretical yield of 52.0 g.
(84.40 / 100) x 52.0 = 43.888 g actual.
Example 3 — Find theoretical yield
You recovered 43.89 g at 84.40% yield.
43.89 / (84.40 / 100) = 52.00 g theoretical.
Example 4 — Multi-trial average
Three trials: 84.40%, 79.23%, 91.35%.
Mean = 84.99%, range = 12.12 percentage points.
How percent yield works
Theoretical yield comes from stoichiometry: convert the limiting reactant to moles, apply the mole ratio from the balanced equation, and convert to grams with the molar mass. Actual yield is what you weigh after purification. Dividing the two gives the fraction of the ideal outcome you achieved; multiplying by 100 expresses it as a percentage.
Because percent yield is a ratio, the units cancel — grams over grams and moles over moles give the same answer. Only when you mix units do you need a conversion, which is why this calculator asks for a molar mass in that case.
Frequently asked questions
What is the percent yield formula?
Percent yield equals actual yield divided by theoretical yield, times 100. As a formula: percent yield = (actual yield / theoretical yield) x 100. For example, if you isolated 43.89 g of product and the balanced equation predicts 52.0 g, the percent yield is (43.89 / 52.0) x 100 = 84.40 percent.
What is the difference between actual yield and theoretical yield?
Theoretical yield is the maximum mass of product the balanced chemical equation predicts if every reactant molecule converted perfectly with zero losses. Actual yield is the mass you really isolated in the lab after filtration, drying, and purification. Percent yield compares the two, so it measures how efficiently the real reaction approached the ideal one.
How do you calculate percent yield from grams?
Weigh your dried, purified product in grams for the actual yield, compute the theoretical yield in grams from the limiting reactant and the balanced equation, then apply (actual / theoretical) x 100. Both values must use the same unit. This calculator checks that for you and converts moles to grams when you enter a molar mass.
Can percent yield be calculated with moles instead of grams?
Yes. Because percent yield is a ratio, any consistent unit works: grams over grams, or moles over moles, give the same answer. If you mix units, enter the molar mass and this calculator converts everything to grams first. For instance, 1.25 mol of a product with molar mass 40 g/mol equals 50.0 g.
What does it mean if percent yield is over 100 percent?
A percent yield above 100 percent is physically impossible for a pure product, so it signals an experimental problem: the product is probably still wet, contaminated with solvent or unreacted starting material, or a mass was misrecorded. For example, 60 g recovered against a 52.0 g theoretical maximum gives 115.38 percent, which means the sample needs drying or repurification, not celebration.
Why is percent yield usually less than 100 percent?
Real reactions rarely reach the theoretical maximum. Common causes are incomplete conversion of reactants, competing side reactions that make unwanted products, and mechanical losses during transfer, filtration, washing, and purification. A yield around 84.40 percent, as in the 43.89 g out of 52.0 g example above, is typical for an ordinary lab synthesis.
How do I find the actual yield if I know the percent yield?
Rearrange the formula to actual yield = (percent yield / 100) x theoretical yield. For example, a reaction with 84.40 percent yield and a theoretical yield of 52.0 g gives an actual yield of (84.40 / 100) x 52.0 = 43.888 g. Use the reverse solver tab above to do this calculation instantly.
How do I find the theoretical yield from percent yield and actual yield?
Rearrange the formula to theoretical yield = actual yield / (percent yield / 100). If you recovered 43.89 g at 84.40 percent yield, the theoretical yield was 43.89 / (84.40 / 100) = 52.00 g. This is useful when a paper reports only the percent yield and the isolated mass.
How do I average percent yield across multiple trials?
Calculate the percent yield for each trial separately, then take the arithmetic mean. With three trials giving 84.40, 79.23, and 91.35 percent, the average is 84.99 percent, with a range of 12.12 percentage points. Reporting the mean together with the range shows both typical performance and reproducibility. The multi-trial tab above does this automatically.
What is the relationship between limiting reactant and percent yield?
The theoretical yield is always calculated from the limiting reactant, which is the reactant that runs out first and caps how much product can form. To find it, convert each reactant to moles, divide by its stoichiometric coefficient, and take the smallest result. If you need that step, use a limiting reactant calculator first, then bring the theoretical yield here. This calculator starts where that one ends: actual versus theoretical.
What is the difference between percent yield, percent recovery, and percent purity?
Percent yield compares product made to product predicted by a chemical reaction. Percent recovery compares mass recovered to mass started with in a purification step like recrystallization, with no reaction involved. Percent purity is the fraction of a sample that is the desired compound, usually from titration or chromatography. They answer different questions, so they are not interchangeable.
What is atom economy and how is it different from percent yield?
Atom economy is a theoretical property of the balanced equation: the molar mass of the desired product divided by the total molar mass of all reactants, times 100. It tells you how wasteful the reaction design is before you ever run it. Percent yield is experimental: how much of that theoretical promise you actually achieved. A green process wants both numbers high.
Can you show a worked percent yield example step by step?
Step 1: write the balanced equation and find the limiting reactant. Step 2: convert the limiting reactant to moles of product using the mole ratio, then to grams using the molar mass. That is the theoretical yield, here 52.0 g. Step 3: weigh the purified product. Here the actual yield is 43.89 g. Step 4: divide 43.89 by 52.0 to get 0.8440, then multiply by 100. The percent yield is 84.40 percent.
Does this calculator convert between grams and moles?
Yes. Set each input to grams or moles independently. When the two units differ, a molar mass field appears and the calculator converts moles to grams before dividing, so the ratio stays valid. All conversions use the molar mass you enter, shown in the step-by-step working so you can verify it.
Is percent yield the same as conversion or reaction efficiency?
Not exactly. Conversion is the fraction of a reactant that was consumed, and reaction efficiency is a loose term that can mean different ratios in different contexts. Percent yield specifically means isolated product divided by the stoichiometric maximum. A reaction can have 100 percent conversion but only 60 percent yield if half the converted material went to side products or was lost in workup.
Educational tool. Results are only as good as your measurements — dry and purify products before weighing, and double-check the balanced equation behind your theoretical yield.
Free tool by NRTechStudio