How to calculate percent error
% error = |Measured − True| ÷ |True| × 100
Worked example. Percent error: 2.141%.
Example inputs — Measured (experimental) value: 9.6; True (accepted) value: 9.81. Starting values are illustrative.
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
Percent error shows how far a measurement is from the accepted value, as a share of that value. The signed error tells you whether you were over (+) or under (−).
Assumptions & limitations
- Results are rounded for display.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
Is percent error the same as percent change?
They use similar math, but percent error compares to a known true value while percent change compares old to new.