# Percentage Error Calculator

LAST UPDATE: April 8th, 2018

## How to Calculate Percentage Error

Percentage error is found by dividing the error amount by the original estimate, then multiplying that result by 100%.
$\text{Percent Error} = \frac{\text{Error}}{\text{Estimated Value}} \times 100\%$
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:
$\frac{25}{50} \times 100\% = 0.5 \times 100\% = 50%$
Error of 25 from an estimate of 75:
$\frac{25}{75} \times 100\% = 0.333 \times 100\% = 33.3%$
Error of 0.0001 from an estimate of 0.0443
$\frac{0.0001}{0.0443} \times 100\% = 0.002257\times 100\% = 0.2257%$

## 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.