Percent Error — Overview & Calculation

What Is Percent Error?

Percent Error is a calculation that determines how much error occurred during an experiment

There are multiple types of error that cause an increase in the percent error. Error can come from a range of mistakes such as technique or a problem with using the equipment. Error is completely normal, and expected!

The Formula for Calculating Percentage Error Is:

$\,$$\,$ $\,$ $\,$ $\,$ $\hspace{1cm}$$\hspace{1cm}$$\hspace{1cm}$$\hspace{1cm}$$\,$$\,$$\,$$\,$$\,$$\,$$\,$$\,$$\,$$\,$$\,$$\frac{|Accepted - Experimental|}{Accepted}$ X 100%

Experimental Value: The value determined from conducting the experiment

Accepted Value: The value derived from a source (typically a known value that can be found from a reliable source)

Here's A Step-by-Step Example:

The melting point of gold is 1,064°C, however, when a student went to determine the melting point of gold, they measured the melting point to be 1,011°C. What is the percent error?

1) Determine which number is the experimental value and which number is the accepted value

Experimental Value: 1,011°C because this is the value the student found while conducting the experiment

Accepted Value: 1,064 because this is the literature melting point of gold

2) Plug the numbers into the equation

$\left(\frac{\left|1064-1011\right|}{1064}\right)\cdot100\%=4.981\%$

3) Boom you're done!

The percent error for this experiment was 4.981%

Try out a problem!

Visual Percent Error

(Video) Calculating Percent Error

by Professor Dave Explains

In this video, professor Dave explains how to calculate error. There are actually a few types of error that you should know about. Maybe the simplest is absolute error. This is what you get when you subtract the actual value from the measured value. However, this value is not very descriptive.

Instead, we usually present something called the relative error. This value is calculated with the following formula:

$$\text{relative error} = \frac{|\text{measured value} - \text{actual value}|}{\text{actual value}}$$

When we multiply this value by 100, we get the percent error or percentage error.