**Percent error** is the difference between a measured value and a known or accepted value.

You can use the following formula to calculate percent error:

**Percent error = |(known value – measured value) / known value| * 100**

The larger the percent error, the greater the difference between a measured value and a known value.

As an example, suppose the height of some tree is known to be exactly **30** feet but you measure it yourself and declare it to have a height of **29.4** feet.

The percent error of your measurement would be calculated as:

- Percent error = |(known value – measured value) / known value| * 100
- Percent error = |(30 – 29.4) / 30| * 100
- Percent error = .02 * 100
- Percent error =
**2%**

The percent error between the known height of the tree and your measured height of the tree is **2%**.

The following example shows how to use a formula in Excel to calculate percent error.

**Example: Calculate Percent Error in Excel**

To calculate percent error in Excel, you must type the known value in one cell and your measured value in another cell.

For example, we will type our known height of **30** in cell **A2** and our measured height of **29.4** in cell **B2**:

We can then type the following formula into cell **C2** to calculate the percent error of our measurement:

=ABS((A2-B2)/A2)*100

The following screenshot shows how to use this formula in practice:

The formula returns **2**, which tells us the percent error between the known value and the measured value is **2%**.

If you would like to display the percentage symbol in the result, you can type the following formula into cell **C2** instead:

=ABS((A2-B2)/A2)*100

This will return **.02** as a result:

You can then select cell **C2** and then click the **Number Format **dropdown menu within the **Number** group on the **Home** tab along the top ribbon and then click **Percentage**:

This will display the result of the formula in a percentage format:

**Additional Resources**

The following tutorials explain how to perform other common operations in Excel:

How to Find the Top 10% of Values in an Excel Column

How to Calculate Cumulative Percentage in Excel

How to Multiply Column by a Percentage in Excel