Percent Error Calculator
Calculate percent error between an experimental and a true value.
Percent error measures how far an experimental or measured value strays from the true or accepted value — a standard way to express measurement accuracy in science and engineering.
Why absolute value is used
Percent error is typically expressed as an absolute value (always positive), since the focus is on the magnitude of the discrepancy, not whether the measurement came in high or low — some fields do track the sign separately when direction of error matters.
Frequently asked questions
What's considered a "good" percent error?
It depends entirely on the field and the precision of the equipment involved — under 5% is often considered acceptable in many educational lab contexts, but professional and industrial contexts often demand far tighter tolerances.
Is percent error the same as percent difference?
No — percent error compares a measured value against a known true value, while percent difference compares two measured values against each other with no assumed "correct" answer.