Math & Statistics
Percent Error Calculator
Measure the absolute difference between an observed value and an accepted value as a percentage of the accepted value. The calculator uses percent error = |observed − accepted| ÷ |accepted| × 100. It returns more than one result so you can check the main answer against a useful secondary measure. The sign of raw error shows direction, while percent error usually reports magnitude. Percent error is undefined when the accepted value is zero; use absolute error instead.
Check the displayed units, assumptions, and rounding before relying on the result.
Calculate and compare
Use the number box for precision or the slider for fast scenario testing.
Scenario results
Percent error
2.6%
Absolute error relative to the accepted magnitude.
Signed error
-2.6
Positive means observed is higher.
Within entered uncertainty
No
Compared with ±1.2.
How the calculation works
Use consistent units and retain full precision until the final display step.
Worked example
Reproduce the displayed scenario, then change one assumption at a time.
Assumptions behind the result
- • Inputs use the units shown beside each control.
- • The displayed formula is applied without hidden market or demographic data.
- • Rounding occurs only for display; calculations keep full numeric precision.
- • The sign of raw error shows direction, while percent error usually reports magnitude.
- • Percent error is undefined when the accepted value is zero; use absolute error instead.
Mistakes that change the answer
- • Mixing percentages with decimals or mixing incompatible units.
- • Relying on a rounded intermediate value instead of the full result.
- • Changing several assumptions at once instead of testing observed value separately.