# Percent Error and Percent Difference

## Percent Error

When comparing an experimental result to a value determined by theory or to an accepted known value (likeg = 9.8 m/s

we determine the difference between the experimental value and the theoretical value as a percentage of the theoretical value. In the definition below, "theoretical" is the value that is determined from theory (i.e., calculated from physics equations) or taken as a known or accepted value like ^{2})*g*.