The Percent Error Calculator helps you determine how far a measured or observed value differs from the true or accepted value.

Percent error is widely used in science, engineering, statistics, and quality control because it offers a clear way to express the accuracy of a measurement.

This calculator performs the percent error formula for you so you can quickly assess how close your results are to the expected value.

What percent error measures

Percent error compares the difference between what you measured and what the value should be.

It shows the size of the error in relation to the true value, expressed as a percentage. This helps you understand whether the variation is small, moderate, or significant.

Percent error is especially common in:

• Lab experiments
• Scientific data collection
• Sensor and instrument calibration
• Construction and engineering measurements
• Manufacturing tolerance checks
• Statistical evaluations

Any situation that requires accuracy or comparison between expected and actual outcomes benefits from percent error.

The percent error formula

The calculation follows a simple structure:

• Subtract the observed value from the true value.
• Take the absolute value of the difference.
• Divide by the true value.
• Multiply by 100 to convert to a percentage.

This calculator completes all of these steps instantly once you enter your inputs.

Why percent error matters

Having a clear error percentage helps you judge whether a measurement is reliable.

A smaller percent error means the observed value is very close to the accepted value.

A larger percent error may suggest measurement inaccuracies, equipment issues, or procedural variations.

Researchers, engineers, and technicians often use percent error to validate results or identify when further investigation is needed.

Tips for better accuracy

While errors cannot always be avoided, you can often reduce them by:

• Calibrating tools before measuring
• Recording measurements carefully
• Repeating tests to confirm consistency
• Measuring under stable conditions whenever possible

Cleaner input data leads to more meaningful error percentages.

Try the Percent Error Calculator

Enter the true value and the observed value.

The tool will calculate the percent error automatically so you can evaluate the accuracy of your results quickly and confidently.