🧪 Percent Error Calculator
In a lab, percent error shows how far your measurement is from the accepted value.
Percent error
How the Percent Error Calculator works
The difference between measured and actual values is divided by the actual value and turned into a percentage. The absolute value is used so the error is positive.
Percent error = |Measured − Actual| ÷ |Actual| × 100
Step-by-step calculation
- 1Enter measured and actual values.
- 2Subtract and take the absolute value.
- 3Divide by the actual value and multiply by 100.
Worked example
Measuring gravity as 9.6 m/s² when the accepted value is 9.81 m/s²: |9.6 − 9.81| ÷ 9.81 × 100 = 2.14%.
Percent Error Calculator examples
| Measured value | Percent error |
|---|---|
| 4.8 | 51.07% |
| 7.2 | 26.606% |
| 9.6 | 2.141% |
| 12 | 22.324% |
| 14.4 | 46.789% |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Percent Error Calculator?
Report lab accuracy correctly.
Important factors that can affect your results
- Which value is the accepted one.
- Sign conventions.
- Measurement precision.
Frequently asked questions
Can percent error be negative?
With the absolute value it is always positive. Some teachers keep the sign to show whether you were over or under.
What is a good percent error?
It depends on the experiment; under 5% is often considered good in school labs.
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Last reviewed November 2026 · How we build and check our tools · Report a problem