How to calculate percentage error

Updated July 20, 2017

The calculation for percentage error is used to evaluate the degree of error in calculations and data. The calculation for percentage error is simple and straightforward. Here are the steps for assessing percentage error.

The formula for calculating per cent error is: estimated value - actual value / actual value * 100%.

Subtract the actual value, the correct value, from the value that is your estimated value. The result may be a negative value, however leave it as a negative. The result is known as the absolute error.

Divide the absolute error, which you calculated from the previous step by the actual value. The result should be a number that is less than 1, such as: 0.11 or 0.95. The resulting value is known as the relative error.

To find the value of per cent error, multiply the relative error from the previous step by 100%. Don't forget to include a per cent sign after the numerical portion of the answer.

Things You'll Need

  • Paper and pencil, or
  • Calculator
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