The Percent Yield Calculator calculates the percentage of product obtained from a chemical reaction compared with the amount that was expected theoretically. It is useful for chemistry students, laboratory work, and anyone checking the efficiency of a reaction.
Percent yield uses two values: the actual yield, which is the amount of product actually obtained, and the theoretical yield, which is the maximum amount expected from the reaction based on stoichiometric calculations. Enter both values into the calculator to get the percent yield instantly.
Quick Answer: Percent Yield Formula
Percent Yield = (Actual Yield Γ· Theoretical Yield) Γ 100%
For example, if the actual yield is 8 g and the theoretical yield is 10 g, the percent yield is 80%.
What Is Percent Yield?
Percent yield is a measure of how much product was obtained compared with the maximum amount predicted by the theoretical calculation. It is expressed as a percentage.
A percent yield close to 100% means the amount collected was close to the theoretical amount. A lower percentage can result from incomplete reactions, side reactions, or product losses during steps such as filtration, transfer, washing, or purification.
In practical laboratory experiments, a percent yield below 100% is common because real experiments rarely recover every possible particle of the desired product.
Percent Yield Formula
The standard formula for calculating percent yield is:
Percent Yield = (Actual Yield Γ· Theoretical Yield) Γ 100%
The actual yield and theoretical yield should be expressed using the same unit. For example, you can use grams for both values or moles for both values. If the units are different, convert them before applying the formula.
How to Calculate Percent Yield
To calculate percent yield manually, divide the actual yield by the theoretical yield and multiply the result by 100.
For example, suppose a reaction has a theoretical yield of 20 g and produces an actual yield of 16 g.
Percent Yield = (16 Γ· 20) Γ 100 = 80%
Therefore, the experiment produced 80% of the theoretically expected amount.
How to Use the Percent Yield Calculator
- Enter the actual yield, which is the amount of product obtained from the experiment.
- Enter the theoretical yield, which is the expected maximum amount of product.
- Make sure both values use the same unit.
- Click the Calculate button.
- Check the resulting percent yield.
You can enter whole numbers or decimal values. The theoretical yield must be greater than zero because division by zero is not valid.
Percent Yield Examples
Working through examples makes the formula easier to understand. The following examples show how different actual and theoretical yields affect the final percentage.
Example 1: 80% Yield
The theoretical yield is 12.0 g and the actual yield is 9.6 g.
Percent Yield = (9.6 Γ· 12.0) Γ 100 = 80%
The experiment recovered 80% of the theoretically expected product.
Example 2: 86% Yield
The theoretical yield is 25.0 g and the actual yield is 21.5 g.
Percent Yield = (21.5 Γ· 25.0) Γ 100 = 86%
The actual product represents 86% of the theoretical yield.
Example 3: Yield Above 100%
Suppose the theoretical yield is 5.00 g and the measured actual yield is 5.10 g.
Percent Yield = (5.10 Γ· 5.00) Γ 100 = 102%
A calculated value above 100% usually indicates an issue with the measurement or sample purity. For example, the product may still contain solvent or moisture, or impurities may have been included in the measured mass.
Percent Yield Reference Table
| Actual Yield | Theoretical Yield | Percent Yield |
|---|---|---|
| 4.0 g | 5.0 g | 80% |
| 7.5 g | 10.0 g | 75% |
| 9.0 g | 10.0 g | 90% |
| 18.0 g | 20.0 g | 90% |
| 22.5 g | 25.0 g | 90% |
| 48.0 g | 50.0 g | 96% |
The table provides a few common examples for quick reference. For other values, enter the actual and theoretical yields into the calculator.
Actual Yield vs Theoretical Yield
Theoretical yield is the maximum amount of product expected from a chemical reaction based on the balanced equation and the available reactants. It is normally determined using stoichiometry and the limiting reactant.
Actual yield is the amount of product that is actually collected or measured after the experiment. It may be lower than the theoretical yield because some material can be lost during the reaction or during the recovery and purification process.
The Percent Yield Calculator compares these two values. It does not calculate the theoretical yield from a chemical equation, so that part of the chemistry must be determined separately when required.
Why Is Percent Yield Usually Below 100%?
A percent yield below 100% does not necessarily mean the experiment failed. Several normal laboratory factors can reduce the amount of product recovered.
- Some reactants may not react completely.
- Side reactions may produce unwanted substances.
- Product can be lost during filtration or transfer.
- Some product may remain on glassware or filter paper.
- Purification steps can remove a small amount of the desired product.
- Measurement errors can affect the recorded actual yield.
The expected yield range depends on the particular reaction, materials, and laboratory procedure, so a lower percentage should be interpreted in that specific context.
Why Can Percent Yield Be More Than 100%?
A calculated percent yield above 100% generally indicates that the measured actual yield is too high relative to the theoretical yield. It does not mean that the reaction created more product than the theoretical maximum predicted by the stoichiometric calculation.
Common causes include:
- Moisture or solvent remaining in the product.
- Impurities mixed with the desired product.
- An incorrect theoretical yield calculation.
- An incorrect limiting reactant or molar mass.
- Errors in recording or measuring the actual yield.
If your result is above 100%, review the theoretical yield calculation and check whether the product was completely dry and sufficiently pure before weighing it.
What Is a Good Percent Yield?
There is no single percentage that is considered good for every chemical reaction. The expected yield depends on the reaction, materials, equipment, purification method, and experimental conditions.
A result should be compared with the expected performance of the particular reaction or laboratory procedure rather than judged against a universal target. In a classroom experiment, your instructor or lab manual may provide an expected range for comparison.
Tips for Getting an Accurate Percent Yield
- Use the same unit for both actual and theoretical yield.
- Check the balanced chemical equation before calculating theoretical yield.
- Identify the correct limiting reactant.
- Use accurate measurements when determining the actual yield.
- Make sure the product is properly dried when the procedure requires it.
- Keep additional digits during intermediate calculations and round the final answer according to your laboratory requirements.
Important Note
This Percent Yield Calculator is designed for educational purposes and general chemistry calculations. It calculates the percentage from the actual and theoretical yield values you provide. For laboratory work, follow the instructions for your specific experiment, including requirements for significant figures, measurement accuracy, and reporting results.