Percent Error Calculator

Compare a measured value with the accepted value and see the percent error, the absolute difference and the signed deviation.

Percent error calculator

Experimental (measured) value

Theoretical (accepted) value

Percent error: —

Signed deviation: —

Absolute difference: —

—

Percent error is reported as a positive magnitude, while the signed deviation keeps the direction of the difference.

Common questions about the free online percent error calculator.

Percent error compares an experimental value with a theoretical or accepted value and reports the gap as a percentage.

Percent error is the absolute difference between the experimental and theoretical values divided by the theoretical value, times 100.

Percent error is reported as a positive magnitude, while the signed deviation keeps the direction of the difference.

A common percent error figure is never negative. The signed deviation is negative when the measured value is below the accepted value.

Percent error is undefined when the accepted value is zero, because the formula divides by that value. The tool says so clearly.

The closer the result is to zero, the better the agreement. Anything under about five percent is often treated as good in a lab.

No. The calculation happens entirely in your browser, so your measurements never leave your device or reach a server.

Yes. It is free to use, needs no sign-up, and you can check as many measurements as you like.

Last updated: October 10, 2026