# Percentage Error Calculator

LAST UPDATE: September 24th, 2020

## Definition – What is a percentage?

A percentage is a number expressed as a fraction of 100.
If a number is 100% (100 percent), then it is a “whole” – the same as one.
If a number is 50%, then it is a half – the same as 0.5 or 1/2.
If a number is 400%, then it is 4 times, the same as 4.

## Formula – How to Calculate Percentage Error

Percentage error is found by dividing the error amount by the original estimate, then multiplying that result by 100%.

Percent Error = (Error ÷ Estimated Value) x 100%

Note: the percent error measures FROM the first value. An error of 25 from an estimate of 50 25 is 50%. If that error were looked at from the perspective of the actual amount (75) it would be a different percentage change (an error of 25 from a result of 75 is a difference of 33.3%).

### Example

Error of 25 from an estimate of 50:
(25 ÷ 50) x 100% = 0.5 x 100% = 50%
Error of 25 from an estimate of 75:
(25 ÷ 75) x 100% = 0.333 x 100% = 33.3%
Error of 0.0001 from an estimate of 0.0443
(0.0001 ÷ 0.0443) x 100% = 0.002256 x 100% = 0.2257%