01
How to use this calculator
- Identify the observed and accepted values in the same units.
- Find the absolute difference between them.
- Divide by the absolute accepted value and multiply by 100.
02
A little understanding goes a long way.
Absolute percentage error expresses the size of a measurement discrepancy relative to a reference. Percentage error is undefined for an accepted value of zero.
THE FORMULA
Percent error = |observed − accepted| ÷ |accepted| × 100
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A worked example
An observed value of 98 compared with an accepted value of 100 has absolute percentage error |98 − 100|/100 × 100 = 2%.
03
A few common questions
Can percent error exceed 100%?
Yes. The absolute discrepancy can be greater than the magnitude of the accepted value.
Is percentage difference the same?
No. Percentage difference commonly uses the average of two values as its denominator, whereas percent error uses a reference value.