Percent Error Calculator
Compare a measured value with a non-zero reference using absolute percent error.
Your result
MATHEnter your values and select calculate.
On this page How it works & practical examples
How to use the Percent Error Calculator
Enter a measured or estimated value and the value you are using as the reference. The percentage uses the reference magnitude as its denominator. The result also retains the signed difference, which tells you whether the measurement is above or below the reference. This separates the direction of error from its magnitude.
The calculation
Worked example
A measurement of 10 against a reference of 12 has absolute error 2 and percent error 16.6667%. The signed difference is −2.
Assumptions and limits
The reference must be non-zero. A reference very close to zero can produce a large percentage even for a small absolute difference. Percent error is not the same as percentage change, relative standard deviation or measurement uncertainty. It does not tell you whether a measurement is acceptable without a tolerance or a relevant experimental context.
Common questions
Can percent error be greater than 100%?
Yes. The absolute difference can exceed the reference magnitude.
Why is a zero reference rejected?
The formula divides by the reference magnitude. With a zero denominator, no finite percentage is defined.