Percentage Error Calculator
Compare an observed value to a true value and get both the signed percent error and absolute percent error. Useful for lab reports, calibration checks, and quality control.
The result you measured, estimated, or predicted.
The accepted, theoretical, or reference value.
Formula
Percent error = ((Observed - True) / True) × 100
Run the calculation to see signed and absolute error measures.
1. Subtract the true value from the observed value.
2. Divide that difference by the true value.
3. Multiply by 100 to convert the ratio into a percent.
Percent error formula
Percent error = ((Observed - True) / True) × 100
The numerator measures the raw difference. Dividing by the true value turns that raw difference into a relative comparison, which makes results easier to compare across different scales.
How to interpret the result
Frequently asked questions
What is percentage error?
Percentage error measures how far an observed or measured value is from a known true value relative to that true value. It is commonly used in science labs, engineering checks, and data validation.
Why can percentage error be negative?
The signed formula keeps direction. A negative result means the observed value is below the true value, while a positive result means the observed value is above it.
What is the difference between percentage error and absolute percent error?
Percentage error keeps the sign, so it shows whether you overestimated or underestimated. Absolute percent error removes the sign, so it only shows how large the error is.
Related Calculators
Percentage Calculator
Calculate percentage of a number, percentage change, and more.
Standard Deviation Calculator
Calculate population and sample standard deviation, variance, and mean.
P-Value Calculator
Calculate statistical significance for various tests.
InvNorm Calculator
Find z-scores, critical values, and x-values from normal probabilities.
Share This Calculator
Found this tool helpful?
Help others discover it with one click.
Copy Link
Suggested hashtags: #percentage #error #Calculator #FreeTools #AICalculator