Percentage Error Calculator
Calculate percentage error between an estimated or measured value and the actual value.
About the % Error Calculator
Percentage error is a standard measurement used in science, engineering, and statistics to express how far an estimated or measured value strayed from the true or accepted value, always as a positive percentage of the true value.
How It Works
The calculator subtracts the actual value from the estimated value, takes the absolute value of that difference, then divides by the absolute value of the actual figure and multiplies by 100.
Percentage Error (%) = |Estimated − Actual| / |Actual| × 100.
Example
Scenario: A measurement of 98 against a true value of 100.
Result: A percentage error of 2%.
Assumptions & Limitations
- Assumes the 'actual' value is the accepted true or reference value, and the 'estimated' value is what was measured or predicted.
- The result is always reported as non-negative, since percentage error measures the size of the deviation, not its direction.
- If the actual value is zero, percentage error is mathematically undefined since you cannot divide by zero.
Frequently Asked Questions
What is considered a low percentage error?
Acceptable percentage error thresholds vary by field — a physics lab experiment might target under 5%, while some engineering applications require far tighter tolerances, so context determines what counts as 'low'.
Is percentage error the same as percentage difference?
They use similar math, but percentage error specifically compares a measured or estimated value against a known true value, while percentage difference compares two values with no designated 'correct' answer.
Does the direction of the error matter?
Percentage error as calculated here reports magnitude only; if you need to know whether the estimate was too high or too low, look at the sign of (Estimated − Actual) before taking the absolute value.