Math Calculators
Percent Error Calculator
Compare a measured value to the true value.
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About the Percent Error Calculator
Percent error measures how far a measured value falls from the true value, as a percentage. Enter the exact value and your measured value and the calculator returns the percent error using |measured − exact| ÷ |exact| × 100. It's a staple of chemistry, physics, and any lab where you compare an experimental result to a known standard.
How to use the Percent Error Calculator
- 01Enter your exact value and measured value.
- 02Read the result instantly — it recalculates as you type.
- 03Adjust the numbers to model different scenarios.
Frequently asked questions
What is the percent error formula?
Percent error = |measured − exact| ÷ |exact| × 100. It's always reported as a positive percentage.
What is a good percent error?
It depends on the experiment — under 5–10% is often acceptable in a classroom lab, while precision work demands far less.