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Percent Yield Calculator

Calculate the percent yield of a chemical reaction from the actual yield you measured and the theoretical yield you expected.

What this tool does

Calculate the percent yield of a chemical reaction from the actual yield you measured and the theoretical yield you expected. You fill in these fields: Actual yield (measured) and Theoretical yield (calculated). It shows percent yield.

Inputs

  • Actual yield (measured): A number. Must be at least 0. The amount of product you actually collected. Use the same unit as the theoretical yield, such as grams.
  • Theoretical yield (calculated): A number. Must be at least 0. The most product the reaction could make, from the balanced equation. Use the same unit as the actual yield. It cannot be 0.

How to use

  1. Enter the actual yield (measured).
  2. Enter the theoretical yield (calculated).
  3. Read the result: percent yield. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Actual yield (measured): 45
  • Theoretical yield (calculated): 50

Results:

  • Percent yield: 90.0%

How this is worked out: Percent yield = (actual / theoretical) x 100 = (45 / 50) x 100 = 0.9 x 100 = 90.

Example 2. Inputs:

  • Actual yield (measured): 30
  • Theoretical yield (calculated): 50

Results:

  • Percent yield: 60.0%

How this is worked out: Percent yield = (30 / 50) x 100 = 0.6 x 100 = 60.

Example 3. Inputs:

  • Actual yield (measured): 45
  • Theoretical yield (calculated): 80

Results:

  • Percent yield: 56.3%

How this is worked out: Percent yield = (45 / 80) x 100 = 0.5625 x 100 = 56.25.

Example 4. Inputs:

  • Actual yield (measured): 1
  • Theoretical yield (calculated): 3

Results:

  • Percent yield: 33.3%

How this is worked out: Percent yield = (1 / 3) x 100 = 33.3333... The expected value is rounded to six decimals, so the tolerance is 0.0001.

Where this comes from

Percent yield of a reaction. The actual yield is taken as a percent of the theoretical yield.

What percent one number is of another. The part is multiplied by 100 and divided by the whole. The whole cannot be 0. Source: Arithmetic: a percent is a number of parts in one hundred, so part / whole x 100.

Limitations

  • Divides the actual yield by the theoretical yield. It does not work out the theoretical yield from a balanced equation.
  • Does not account for side reactions, reagent purity or product lost during transfer, because those are not part of the two numbers entered.
  • Both yields must be in the same unit. The tool does not convert units.

FAQs

Q: What unit should I enter?
A: Enter both yields in the same unit, such as grams or moles. The percent is a ratio, so the unit cancels out, but mixing units gives a wrong answer.
Q: Can the percent yield be over 100?
A: Yes. If the actual yield is larger than the theoretical yield, the tool shows a percent over 100 and a warning. This can happen when the product still holds water or other impurities, or when a measurement is off.
Q: Where does the theoretical yield come from?
A: It is the most product the reaction could make, worked out from the balanced equation and the amount of the limiting reactant. This tool does not calculate it. Enter the value you worked out yourself.

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