Percent Yield Calculator
If a reaction should produce 20 grams of product but you only collect 15.2 grams, the percent yield is 76%. This percent yield calculator compares what a chemical reaction actually produced against what it should have produced in theory, giving you a measure of how efficient the reaction was. Enter any two of the three values (actual yield, theoretical yield, percent yield) and the tool solves for the missing one. Percent yield is one of the most common calculations in chemistry lab courses. It tells you how much product was lost to side reactions, incomplete reactions, transfer losses, and purification steps. A yield of 70 to 90% is typical for many organic synthesis reactions, while yields above 100% usually indicate impurities or measurement error.
Quick answer
Percent yield equals actual yield divided by theoretical yield, multiplied by 100.
What this tells you
- •Percent yield equals actual yield divided by theoretical yield, multiplied by 100.
- •Actual yield is the amount of product you physically collect after the reaction and any purification steps.
- •Theoretical yield is the maximum amount predicted by stoichiometry from the limiting reactant.
- •A percent yield below 100% means some product was lost, which is normal in most reactions.
- •A percent yield above 100% usually means the product contains impurities like residual solvent or unreacted starting material.
- •The calculator works in three modes: find percent yield, find actual yield, or find theoretical yield from the other two values.
How to Use
- 1Choose the mode that matches what you need to find. Most students use the default percent yield mode.
- 2Enter the values you know. For percent yield mode, enter the actual yield and theoretical yield in grams.
- 3Click Calculate to see the missing value along with all three quantities.
- 4If your yields are in moles instead of grams, convert them first. Percent yield works in any unit as long as both values use the same unit.
- 5Compare your result against typical ranges. Below 50% suggests significant losses, 70 to 90% is common, and above 100% suggests contamination.
How It Works
Formula
Percent yield = (actual yield / theoretical yield) x 100The percent yield formula measures reaction efficiency. The actual yield is what you weigh on the balance after the experiment. The theoretical yield comes from a stoichiometry calculation using the limiting reactant and the balanced chemical equation. Dividing actual by theoretical and multiplying by 100 converts the ratio to a percentage. The formula works with any mass unit (grams, milligrams, kilograms) as long as both yields use the same unit, and it also works with moles when both values are in moles. The calculator can rearrange the formula to solve for any one of the three variables: actual yield = (percent yield / 100) x theoretical yield, or theoretical yield = actual yield / (percent yield / 100).
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Standard lab reaction
Divide 15.2 by 20.0 to get 0.76, then multiply by 100 for 76%. This is a reasonable yield for a multi-step organic reaction where some product is lost during purification.
High-yield precipitation
A 98% yield means almost all the theoretical product was recovered. Precipitation reactions with good filtration technique often achieve yields this high because the product separates cleanly from solution.
Find actual yield from 82% yield
Multiply 50 grams by 82/100 to get 41 grams. This is useful when you know the theoretical maximum and the expected efficiency and want to predict how much product to expect before running the experiment.
Find theoretical yield from 12 g actual at 60%
Divide 12 by 60/100 to get 20 grams. This reverse calculation helps when you know the percent yield and the amount collected and want to check whether your stoichiometry calculation was correct.
Typical Percent Yield Ranges by Reaction Type
General ranges observed in undergraduate chemistry labs. Actual results depend on technique, reaction conditions, and product stability.
| Reaction type | Typical yield range | Notes |
|---|---|---|
| Precipitation | 85 to 99% | Product separates cleanly, losses mainly from transfer |
| Acid-base neutralization | 90 to 99% | Often near-quantitative with careful titration |
| Esterification | 50 to 75% | Equilibrium-limited, water removal improves yield |
| Grignard reaction | 55 to 80% | Sensitive to moisture and air |
| Recrystallization recovery | 60 to 85% | Some product stays dissolved in the mother liquor |
| Multi-step synthesis (overall) | 30 to 60% | Losses compound across each step |
These are general guidelines for educational labs. Industrial processes are optimized for much higher yields.
Common mistakes
- Using different units for actual and theoretical yield. If actual is in grams and theoretical is in moles, the ratio is meaningless. Convert both to the same unit first.
- Calculating theoretical yield from the wrong reactant. The theoretical yield must come from the limiting reactant, not the one in excess.
- Reporting a yield above 100% without checking for impurities. Wet product, residual solvent, or unreacted starting material inflate the apparent mass and push the yield above 100%.
- Forgetting to multiply by 100. Dividing actual by theoretical gives a decimal like 0.76, not 76%. The final step is multiplying by 100.
- Rounding intermediate steps too early. Keep full precision through the calculation and round only the final answer to match the least precise measurement.
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