How To Calculate Percent Error – A2Z Calculators

By A2Z Calculators | Last update: 26 December 2023

Welcome to A2Z Calculators, where precision meets simplicity! In the world of scientific measurements, understanding how to calculate percent error is a fundamental skill. Whether you’re navigating the realms of chemistry, working with data sets, or analyzing density values, we’ve got you covered. In this comprehensive guide, we’ll walk you through the step-by-step process of calculating percent error, making it easy for you to grasp this essential concept.

How To Calculate Percent Error

What is Percent Error?

Percent error is a powerful tool used to evaluate the accuracy of your measurements by comparing them to accepted or true values. It’s a way to quantify the difference between what you observed or measured and what the actual value should be. The formula is straightforward:

Percentage Error= (Observed Value − True Value / True Value) × 100%

Step-by-Step Guide:

1. Identify the True Value

Before diving into calculations, pinpoint the accepted or true value that serves as your benchmark. This could be a standard value from a reference source or an expected result.

2. Measure the Observed Value

Obtain your experimental or observed value through measurements, experiments, or calculations. This is the value you’ll be comparing to the true value.

3. Calculate the Difference

Find the difference between the observed and true values. This step quantifies how much your measurement deviates from the expected result.

4. Apply the Formula

Plug the values into the percent error formula. Divide the difference by the true value and multiply by 100 to express the error as a percentage.

5. Round if Necessary

Consider the level of precision needed and round your percentage error to an appropriate number of decimal places.

Example Calculation:

Let’s walk through an example to solidify your understanding. Say you measured the density of a substance, and the accepted density is 8.00 g/cm³. Your measured density is 7.60 g/cm³.

Percentage Error = (7.60 − 8.00 / 8.00) × 100% =−5%

The negative sign indicates that your measured density is lower than the accepted value.

Tips for Success:

  • Precision Matters: Be aware of the precision of your measurements and round your results accordingly.
  • Context is Key: Understand the context of your experiment or analysis to interpret the significance of your percentage error.
  • Average Percent Error: If dealing with multiple measurements, calculate the average percent error for a more comprehensive assessment.


Congratulations! You’ve now mastered the art of calculating percent error. Armed with this knowledge, you can enhance the accuracy of your experiments and measurements. Remember, at A2Z Calculators, we believe in making complex concepts accessible, and percent error is no exception.