# Percent Error Calculator: How Far Off Was The Measurement?

Written by:
PK

Below is a percent error calculator, which will compute the percent error between a measured value and the actual, known value. Enter your measurement and the actual value to see the percent error.

## What is the Percent Error?

Percent error is the difference between a measured, guessed, estimated, or modeled value and the actual value.

For example, you may have modeled a value. Taking your modeled value and comparing it to the actual result using the percent error shows you how much you "were off", expressed as a percentage.

## What is the Percent Error Formula?

The percent error formula is:

\frac{actual-measured}{actual}*100

### Working through a percent error calculation

Let's say that you modeled (or measured) a value of 10 units. However, you later found out the actual value was 8 units:

\frac{8-10}{8}*100\\\frac{-2}{8}*100\\-.25*100=-25\%

You could state the percent error as -25%, or drop the negative sign and state there was a 25% error.

## Using the Percent Error Calculator

To use the percent error calculator, first enter the Actual Value of whatever it is you're measuring. In the Measured Value, enter your guess, observation, measurement, or modeled value in the same units as the actual.

Then, press the Compute Error button and we'll calculate the percent error.