Percent Error Calculator
Calculate the percent error between an observed (experimental) value and a theoretical (accepted) value.
Percent Error Calculator
Calculate the percent error between an observed (experimental) value and a theoretical (accepted) value.
Real-World Examples
You measured gravity as 9.78 m/s² while the accepted value is 9.81 m/s². What is the percent error?
0.31%
You calculated a concentration of 0.095 M while the theoretical value is 0.100 M. What is the percent error?
5%
A part measured 10.2 mm against a theoretical 10.0 mm. What is the percent error?
2%
Common Mistakes to Avoid
Forgetting to take the absolute value of the theoretical value in the denominator
Fix: If the theoretical value is negative, the denominator must still be positive. Use |theoretical| to keep the percent error meaningful.
Reporting a signed percent error as the final answer
Fix: Percent error is conventionally reported as a positive value. The signed difference is useful for knowing whether you over- or under-measured, but the percent error itself uses absolute values.
Dividing by the observed value instead of the theoretical value
Fix: The accepted (theoretical) value is the reference, not your measurement. Dividing by the observed value computes something else entirely.