Percent Error Calculator: Percent Error, Percent Difference and Percent Uncertainty
Check how close a measurement is to the true value.
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How this calculator works
Choose percent error, percent difference or percent uncertainty.
Enter your measured value and the accepted value, or the two measurements, or the measurement and its uncertainty.
The calculator gives the answer with the formula and the absolute and relative error.
Formulas used
- \%\text{ error} = \frac{|\text{measured} - \text{accepted}|}{|\text{accepted}|}\times100
- \%\text{ difference} = \frac{|x_1 - x_2|}{(x_1 + x_2)/2}\times100
- \%\text{ uncertainty} = \frac{\delta x}{x}\times100
Worked example
With the default numbers in the calculator above:
- Percent error: 1.631 %
- Absolute error: 0.16
- Relative error (as a fraction): 0.01631
- Signed percent error (negative if your value is too low): -1.631 %
- Accuracy (100 percent minus the percent error): 98.369 %
Change the numbers in the calculator to see the full working, every step, for your own case.
A second worked example
A different case, with these numbers: What do you want? Percent difference between two measurements.
- Percent difference (the gap as a share of the average of the two values): 1.6444 %
- The difference and the average: 0.16 and 9.73
Common questions
How do I calculate percent error?
Subtract the accepted value from your measured value, take the size of the result, divide by the accepted value and multiply by 100.
What is the difference between percent error and percent difference?
Percent error compares a result with a true value. Percent difference compares two measurements when neither is known to be true.
Can percent error be negative?
The usual formula uses the absolute value, so it is positive. The signed error shows whether you were too high or too low.
Related calculators
Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: Any school science text (error analysis).
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