Percent Error Calculator
Calculate percent error between your experimental and theoretical values instantly with this free percent error calculator.
Enter Values
How to use this calculator
- Enter your measured value and the actual value.
- Read the percent error.
How it works
Percent error = |measured − actual| ÷ |actual| × 100 — how far off the measurement is, relative to the true value.
Worked example
Measured 98, actual 100. |98 − 100| ÷ 100 × 100 = 2% error.
Common mistakes
- Dividing by the measured value instead of the actual one.
- Reporting a negative — percent error uses the absolute difference.
Frequently asked questions
How do I calculate percent error?
Percent error = |measured − actual| ÷ |actual| × 100. It shows how far a measurement is from the true value.
What is a good percent error?
It depends on the field, but under a few percent is often acceptable in school experiments; precision work demands far less.
Is percent error always positive?
Yes — it uses the absolute difference, so it shows the size of the error regardless of direction.
Related tools
- Percentage Change Calculator
- Percentage Difference Calculator
- Percentage Decrease Calculator
- Percentage Increase Calculator
- Fraction to Percent Calculator
- Reverse Percentage Calculator
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Cite this tool
Zerdly. (2026). Percent Error Calculator. Retrieved from https://www.zerdly.com/tools/percent-error-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.