Quick answer
Percent yield = actual yield ÷ theoretical yield × 100. Obtaining 8.2 g from a theoretical 10 g is 82%, a shortfall of 1.8 g.
Enter the actual and theoretical yields. The calculator returns the percent yield and shortfall.
Related tools: Mass Percent Calculator: Mass percent of a component in a mixture or compound. Mole Calculator: Convert between mass, moles and number of particles. Electron Configuration Calculator: Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons.
How to use the Percent Yield Calculator
- Enter actual yield (above 0).
- Enter theoretical yield (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Actual yield | A number | > 0 |
| Theoretical yield | A number | > 0 |
Formula and method
Formula
percent yield = actual ÷ theoretical × 100
IEEE-754 double precision; shown to the decimals indicated.
Use the same unit for both yields.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Actual yield = 8.2; Theoretical yield = 10.
| Result | Value |
|---|---|
| Percent yield | 82% |
| Shortfall | 1.8 |
Example 2
Inputs: Actual yield = 45; Theoretical yield = 50.
| Result | Value |
|---|---|
| Percent yield | 90% |
| Shortfall | 5 |
Example 3
Inputs: Actual yield = 3.3; Theoretical yield = 3.3.
| Result | Value |
|---|---|
| Percent yield | 100% |
| Shortfall | 0 |
The first line is the headline result (percent yield). Below it the percent Yield Calculator lists shortfall, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Why yields fall short
Incomplete reactions, side reactions and losses in purification reduce the actual yield. Many lab syntheses give 50 to 90%; multistep syntheses multiply the losses: three steps at 82% give 55%.
Over 100%
Values above 100% usually mean impurities (for example residual solvent) or errors. The theoretical yield comes from the limiting reagent and the balanced equation.
Interpreting percent yield
8.2 g obtained from a theoretical 10 g is 82%, a shortfall of 1.8 g. The theoretical yield comes from the balanced equation, using the limiting reactant.
A value above 100% points to an impure or wet product or a measurement error, since a reaction cannot create more product than the theory allows.
How the result changes with actual yield
Holding every other input at the first worked example, this table changes only actual yield. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Actual yield | Percent yield | Shortfall |
|---|---|---|
| 4.1 | 41% | 5.9 |
| 8.2 | 82% | 1.8 |
| 16.4 | 164% | -6.4 |
| 32.8 | 328% | -22.8 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Actual yield: entering "0" shows "Actual yield must be greater than 0." beside that field and no result.
- Theoretical yield: entering "0" shows "Theoretical yield must be greater than 0." beside that field and no result.
Choosing between the Percent Yield Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Mass Percent Calculator](/science/mass-percent-calculator/) | mass of component and total mass | Mass percent |
| [Mole Calculator](/science/mole/) | start from and molar mass | Amount |
| [Electron Configuration Calculator](/science/electron-configuration/) | element and charge | Electron configuration of H |
| [Dilution Calculator](/science/dilution-ratio/) | solve for | Final volume V₂ |
| [Molarity Calculator](/science/molarity-calculator/) | solute mass, molar mass and solution volume | Molarity |
Background: chemistry calculations
Most basic chemistry calculations chain three relations: moles n = mass ÷ molar mass, molarity M = n ÷ volume in litres, and dilution C₁V₁ = C₂V₂. Keep units consistent: grams with g/mol, litres with mol/L.
Molar masses come from standard atomic weights, which differ slightly between tables and with the isotopic make-up of a real sample.
Assumptions and limitations
- Values above 100% usually mean impurities or errors
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for actual yield and theoretical yield to confirm this.
Frequently asked questions
How do I find theoretical yield?
Use stoichiometry from the limiting reagent.
Is 82% a good yield?
Yes for many reactions.
What causes yields over 100%?
Wet or impure product.
Can percent yield exceed 100%?
Not in theory. A value above 100% usually means the product is impure, still contains solvent, or was mismeasured.
How do I get the theoretical yield?
Use the balanced equation and the limiting reactant to calculate the maximum product in moles, then convert to mass.
What does the Percent Yield Calculator calculate?
Percent yield of a reaction. It returns Percent yield and Shortfall.
What formula does the Percent Yield Calculator use?
percent yield = actual ÷ theoretical × 100. Use the same unit for both yields.
What do I need to enter in the percent Yield Calculator?
You enter Actual yield and Theoretical yield.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Values above 100% usually mean impurities or errors.
What is an example of a percent Yield result?
With actual yield 8.2 and theoretical yield 10, the percent yield is 82%.
Where does the method come from?
The method follows: OpenStax, Chemistry 2e (Rice University): stoichiometry and percent yield.
Related calculators
- Mass Percent Calculator — Mass percent of a component in a mixture or compound.
- Mole Calculator — Convert between mass, moles and number of particles.
- Electron Configuration Calculator — Ground-state electron configuration of an element or monatomic ion, with noble-gas shorthand and unpaired electrons.
- Molarity Calculator — Concentration of a solution from solute mass, molar mass and volume.
- Average Atomic Mass Calculator — Weighted average of isotope masses.
Sources
- OpenStax, Chemistry 2e (Rice University): stoichiometry and percent yield
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.