Percent Error Calculator
Calculate the percent error between the measured value and the true value.
Tip: % error = |measured value − true value| ÷ true value × 100.
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About this digital tool
The percent error calculator compares a measured value with the true or theoretical value and shows how far off the measurement is. Enter the measured value and the true value and get the percent error as well as the absolute error. The true value cannot be zero.
The formula is: percent error = |measured value − true value| ÷ |true value| × 100. If a scale shows 9.8 kg for an object of 10 kg, the absolute error is 0.2 kg and the percent error 0.2 ÷ 10 × 100 = 2%. It is used in physics and chemistry labs, in engineering, in quality control and in school assignments to assess the accuracy of a measurement or a calculation.
How to use
- Enter the value measured in your experiment or calculation.
- Enter the true or theoretical value, which must not be zero.
- Read the percent error in the result bar.
- Compare with the absolute error to see how many units the measurement is off.
Frequently asked questions
How is percent error interpreted?
The closer to 0%, the more accurate the measurement. E.g. a 2% error shows high accuracy; 20% shows a considerable deviation.
How is percent error calculated?
Subtract the true value from the measured one, take the absolute value, divide by the true value and multiply by 100. E.g. measured 98 and true 100 gives 2 ÷ 100 × 100 = 2%.
What is the difference between absolute and relative error?
Absolute error is the simple difference, e.g. 2 units. Relative error divides it by the true value and, multiplied by 100, becomes the percent error.
Why can't the true value be zero?
Because the formula divides by the true value, and division by zero is undefined. In that case you should use the absolute error.