Percent Error Calculator
Enter your measured value and the true (accepted) value.
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Formula
Percent error = |measured − true| ÷ |true| × 100. If you measure gravity as 9.6 m/s² against the accepted 9.81 m/s², the percent error is 2.14%.
The other values
- Absolute error — the size of the difference, in the original units.
- Signed error — positive if the measurement was too high, negative if too low; useful for spotting a systematic bias.
- Relative error — the percent error as a fraction.
Percent error vs percent difference
Percent error compares a measurement with a known correct value. When neither value is "correct" (two students' measurements), use percent difference instead — the difference divided by the average of the two. For lab reports, also discuss the likely sources of error, such as instrument precision, reaction time or temperature.
Free to useNo software to install — works in any modern browser.
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How it works
- Enter — type or paste your values or text.
- Get the result — it is worked out in your browser.
- Adjust — change the inputs to compare, or copy the result.
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