Percent Error Calculator

Percent error compares a measurement to the accepted value: |measured − true| ÷ |true| × 100. Measuring gravity at 9.5 m/s² against 9.81 gives 3.2% error. It normalizes by the true value, so errors are comparable across quantities of different sizes.

Percent error needs a known true value — lab class territory. Real research often has no accepted answer, so scientists report uncertainty (the spread of repeated measurements) instead. Precision without accuracy is the classic trap: consistent and consistently wrong.