Percent Error Calculator
Percent error calculator: compare a measured value with the true value to get percent error and absolute error for labs.
Editorial review: Farrow (pseudonym; identity and professional credentials are not disclosed). This page is for educational purposes, not professional advice.
Your inputs
Results update as you type. Nothing you enter leaves your device.
Results
- Absolute error
- 0.21
- Signed error
- -2.141%
Example with the starting values
These results use the calculator's initial inputs. Change the values above to calculate your own estimate.
Inputs
- Measured (experimental) value
- 9.6
- Actual (accepted) value
- 9.81
Results
- Percent error
- 2.141%
- Absolute error
- 0.21
- Signed error
- -2.141%
How does the Percent Error Calculator work?
Percent error = |measured − actual| / |actual| × 100. If a lab measures gravity as 9.6 m/s² and the accepted value is 9.81, the error is 0.21 / 9.81 × 100 = 2.14%.
The accepted (true) value goes in the denominator, so it cannot be 0. A signed result tells you whether the measurement ran high or low.
Frequently asked questions
What is the percent error formula?
Percent error = |experimental − theoretical| / |theoretical| × 100. Use the accepted value as the theoretical one.
Can percent error be negative?
The standard formula uses absolute value so it is never negative. This calculator also shows the signed error to show over or under.
Percent error or percent difference?
Use percent error when one value is a known true value. Use percent difference when both values are equally uncertain.
What is a good percent error?
It depends on the field. In school labs under 5% is often acceptable and under 1% is very good, while precision engineering needs far less.