Enter the true or accepted value and the observed value into the calculator to determine the percentage accuracy of the test or measurement.

Percentage Accuracy Formula

The following formula is used to calculate the percentage accuracy of a test.

A = 100 - [(Tv-Ov)  / Tv *100]
  • Where A is the percentage accuracy (%)
  • Tv is the true value or theoretical value
  • Ov is the observed or measured value

To calculate a percentage accuracy, subtract the observed value from the true value, divide by the true value, multiply by 100, then subtract this result from 100.

Percentage Accuracy Definition

A percentage accuracy is a measure of how close a measurement or test is to the true or theoretical value of that measurement or test. This is a ratio of the difference between true and measured divided by the true value.

Percentage Accuracy Example

How to calculate a percentage accuracy?

The first step in calculating a percentage accuracy is to determine the true value of the experiment. This would be a known quantity based on a fundamental formula or known data.

In this example, the true value will be set as 5.

The next step is to determine the observed value after the experiment has been performed.

In this case, the observed value is found to be 4.

Lastly, calculated the percentage accuracy of the experiment using the formula above:

%A = 100 – | (Tv-Ov) / Tv *100 |

%A = 100 – | (5-4) / 5 *100 |

%A = 80%

What is a good accuracy percentage?

A good accuracy percentage depends on the test being performed, but the closer to 100% accuracy the better in all cases. For example, a percentage accuracy of a test for a chemical composition through mass spectrometer is expected to be 99+% accurate


What is a percent accuracy?

Percent accuracy is a ratio used to describe how close a measured or observed value of a measurement or test is to the theoretical value.