Percent Error Calculator
Calculate percent error between a measured/estimated value and a known true value, with absolute-error detail.
Runs 100% in your browser — nothing is uploaded.
Result
Formula
Percent error = |observed − true| ÷ |true| × 100
About this calculator
Common in science labs, percent error expresses how far a measurement sits from an accepted value. The sign shows direction; the magnitude is usually what matters.
How to use
- 1
Enter your measured value.
- 2
Enter the accepted value.
- 3
Read percent error instantly.
Frequently asked questions
What is the difference between percentage error and percentage difference?
Percentage error compares an observed value to a known true value, using the true value as the denominator. Percentage difference compares two measured values without a designated true value, using the average of the two as the denominator.
Can percentage error be negative?
In this calculator, percentage error is always positive because we take the absolute value. Some contexts report signed error (positive for overestimation, negative for underestimation), but the standard percentage error is non-negative.
What if the true value is zero?
Percentage error is undefined when the true value is zero because division by zero is not possible. In such cases, use absolute error or relative error with a different reference.
Please note: Results are estimates for general information only and are not professional or medical/financial advice.