Percent Error Calculator
Calculate percent error between a measured value and the true value.
How far off a measurement is
Percent error expresses how much a measured or estimated value differs from the true or accepted value, as a percentage of the true value. This calculates it, the standard way to report the accuracy of an experiment or estimate in science.
Enter the measured and true values to find the percent error.
Accuracy in context
The reason percent error is used rather than the raw difference is that it puts the error in proportion: being off by one unit is trivial when measuring thousands and serious when measuring ten, and the percentage captures that. It is the standard measure of experimental accuracy, telling you how close a result came to what it should be. A small percent error means good accuracy; a large one flags a problem with the measurement or the method. It is worth distinguishing from precision, which is about how repeatable a measurement is rather than how close to the truth — a set of measurements can be precise but consistently wrong, which percent error would reveal.
Common questions
Why use percent error instead of the raw difference?
Because it puts the error in proportion — being off by one unit matters far more when measuring ten than when measuring thousands.
What is the difference between accuracy and precision?
Accuracy is closeness to the true value, which percent error measures; precision is how repeatable measurements are. A result can be precise but inaccurate.
Is anything uploaded?
No. The calculation happens in your browser.