Measure how far an observed value is from a known true value, as a percentage.
Formula
percent error = |observed − true| / |true| × 100%
Explanation
Absolute error is |observed − true|. Relative error divides that by |true|. Percent error multiplies relative error by 100. A signed form without absolute value shows direction (over- or under-estimate).
Variables
observedthe measured or experimental value
truethe accepted or expected reference value
When to use
Lab reports, instrument checks, and comparing an estimate to a known standard.