Calculate the percentage error between an experimental (observed) value and a theoretical (accepted) value. Used in science, lab experiments, and quality control.
This tool calculates the percentage difference between an experimental (measured) value and a theoretical (true or accepted) value, expressing measurement accuracy as a percentage. It's widely used in science experiments, engineering measurements, and quality control.
Percentage Error = |Experimental Value − Theoretical Value| ÷ |Theoretical Value| × 100. The absolute value is used so the result is always expressed as a positive percentage, regardless of whether the measured value was higher or lower than expected.
Enter your experimental (measured) value and the theoretical (accepted or expected) value, and the calculator returns the percentage error.
Example: If a theoretical value is 50 and an experimental measurement gives 47, the percentage error is |47 − 50| ÷ 50 × 100 = 6%.
What is considered an acceptable percentage error? This varies significantly by field and context — some scientific experiments require error under 1-2%, while other estimations tolerate higher error, so acceptability depends on your specific application and precision requirements.
What's the difference between percentage error and percentage difference? Percentage error compares a measured value against a known "true" or theoretical value, while percentage difference compares two values where neither is necessarily considered more correct than the other.
Why is the absolute value used in the formula? Using absolute value ensures the result is always a positive percentage representing the magnitude of the error, regardless of whether the measurement was too high or too low.
Can percentage error be greater than 100%? Yes, if the experimental value is more than double the theoretical value (or close to zero when it shouldn't be), the percentage error can exceed 100%.
How can I reduce percentage error in an experiment? Using more precise instruments, taking multiple measurements and averaging them, controlling environmental variables, and following careful, consistent measurement procedures all help reduce percentage error.