Percent Error Calculator
Calculate the percent error between an experimental (measured) value and a theoretical (accepted) value — commonly used in science and lab work.
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Your result
2.00%
Percent error
AI explanation
Formula
Percent error = |Experimental − Theoretical| / |Theoretical| × 100Worked example
Measured 9.8, accepted value 10
| Field | Value |
|---|---|
| Experimental (measured) value | 9.8 |
| Theoretical (accepted) value | 10 |
| Percent error | 2 |
| Difference (experimental − theoretical) | -0.2 |
Assumptions
- Percent error is conventionally reported as a non-negative magnitude, regardless of whether the measured value was higher or lower than the accepted value.
- The theoretical value cannot be zero.
Frequently asked questions
How is percent error calculated?
Take the absolute difference between the experimental and theoretical values, divide by the absolute value of the theoretical value, then multiply by 100.
Why is percent error always shown as positive?
By convention, percent error reports the magnitude of the discrepancy, not its direction — whether you measured too high or too low, the "difference" field shows the signed value for that context.
What's considered a "good" percent error?
It depends entirely on the field and the precision of the measuring instrument — a percent error acceptable in a rough estimate might be unacceptable in precision engineering or analytical chemistry.