Percent Error Calculator
Compare your experimental (measured) value to the accepted (true) value to calculate percent error. Perfect for science labs.
Free Percent Error Calculator
The SmarterSources Percent Error Calculator helps students and researchers quickly determine the accuracy of experimental measurements. Enter your measured value and the accepted (true) value to see the percent error, absolute error, and relative error.
How to Calculate Percent Error
The formula is: Percent Error = |Experimental - Accepted| / |Accepted| × 100. The absolute value ensures the result is always positive. A lower percent error means your measurement was more accurate.
Understanding Error Types
Absolute error is the simple difference between the two values. Relative error is the absolute error divided by the accepted value (as a decimal). Percent error is the relative error multiplied by 100.
Frequently Asked Questions
What is a good percent error?
Under 5% is generally acceptable for most science experiments. Under 1% is excellent. Acceptable thresholds depend on the precision of equipment and the nature of the experiment.
Can percent error be negative?
The standard formula uses absolute values, so percent error is always positive. Some instructors allow signed error (without absolute value) to show direction. This calculator uses the standard (positive) formula.
Is my data safe?
Yes. This calculator runs entirely in your browser. No data is sent to any server and nothing is stored.