Percent Error Calculator
Enter your measured (experimental) value and the accepted (true or theoretical) value, and the calculator gives the percent error, the signed percent error that shows whether you were too high or too low, the absolute error and the relative error, with the working. A second mode takes a list of measurements and gives each error plus the mean absolute percent error and the mean signed percent error. Everything runs in your browser.
|9.5 - 9.81| / |9.81| x 100 = 0.31 / 9.81 x 100 = 3.16%
Percent error = |measured - accepted| / |accepted| x 100. The accepted value is the one you compare against, so it goes in the denominator, and the answer is always positive. The signed version shows whether the measurement is too high or too low. It is not the same as percent difference, which compares two measurements with neither one accepted as true. Percent error is undefined when the accepted value is 0. Everything runs in your browser.
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Math & MoneyAbout the Percent Error Calculator
Percent error measures how far a measurement is from the value it should have, as a share of that value. The formula is |measured minus accepted| divided by |accepted|, times 100. The absolute error is the size of the difference, the relative error is that difference divided by the accepted value, and the percent error is the relative error as a percentage. For example, if a lab measures gravity as 9.5 and the accepted value is 9.81, the absolute error is 0.31, the relative error is 0.0316 and the percent error is 3.16%, with the measurement 3.16% too low. With three measurements of 9.5, 9.7 and 9.9, the signed errors are -3.16%, -1.12% and +0.92%. The mean absolute percent error is 1.73%, while the mean signed error is -1.12%, which shows a small bias towards low readings. Percent error is not defined when the accepted value is 0, because the formula divides by it. It also differs from percent difference, which compares two measurements when neither is the accepted one.
How do you calculate percent error?▾
Subtract the accepted value from the measured value, take the absolute value, divide by the absolute accepted value and multiply by 100. For 9.5 against 9.81 that is 0.31 / 9.81 x 100 = 3.16%.
Can percent error be negative?▾
The standard percent error is always positive. The signed version keeps the sign, so a negative value means the measurement was lower than the accepted value.
What is the difference between percent error and percent difference?▾
Percent error compares a measurement with an accepted true value. Percent difference compares two values when neither is the true one, so it divides by their average.
What is a good percent error?▾
There is no single answer. It depends on the experiment and the equipment, so check what your teacher, lab manual or field expects. Smaller is better.
Is my data uploaded?▾
No. The calculation runs in your browser and nothing you enter is sent anywhere.