Toolstia / Percent error calculator
Percent error calculator
Percent error shows how far a measurement is from the accepted value, as a percentage of that accepted value. It is used in science labs, engineering and quality checks. Enter both numbers to get the error, with its sign and absolute size.
Enter your measured value and the accepted value. The accepted value cannot be zero.
Percent error = |measured − actual| ÷ |actual| × 100. A negative signed error means the measurement was below the accepted value.
How it works
- Enter the measured (experimental) value.
- Enter the actual (accepted) value.
- Read the percent error and the related figures.
Formula
Percent error = |measured − actual| ÷ |actual| × 100. If you measure 9.5 and the true value is 10, the error is 0.5 ÷ 10 × 100 = 5%.
Signed error
Without the absolute value you get a signed error. A negative sign means the measurement was lower than the accepted value, which tells you the direction of your error.
Percent difference
When neither number is the accepted value, such as two measurements of the same thing, compare them with the percent difference: the gap divided by the average of the two. It is shown as well.
Zero reference
If the accepted value is zero the percentage is undefined, so the tool asks for a non-zero actual value.
Questions
What is a good percent error?
It depends on the field. Many school labs aim for under 5%, while precision work needs far less.
Is it the same as percentage change?
The formula is similar, but percentage change compares an old and a new value rather than a measurement and a true value.
Is anything uploaded?
No. Your numbers stays in your browser and is never sent anywhere.