Percent error is standard in science labs for judging how close an experimental result is to the accepted value.
How to use the Percent Error Calculator
- Measured value
- True value
Results update as you type, and every field accepts the units shown in its menu.
How it works
Subtract the true value from the measured value, take the absolute value and divide by the true value.
Inputs explained
| Field | What to enter |
|---|---|
| Measured value | A number |
| True value | A number |
What each result means
- Percent error = abs([Measured value] – [True value])÷abs([True value]) × 100
- Absolute error = abs([Measured value] – [True value])
- Signed relative error = ([Measured value] – [True value])÷[True value] × 100
Example values
How the main result changes when Measured value changes and everything else stays at the example values above:
| Measured value | Percent error (%) |
|---|---|
| 4.8 | 51.0703 |
| 7.2 | 26.6055 |
| 9.6 | 2.1407 |
| 12 | 22.3242 |
| 14.4 | 46.789 |
| 19.2 | 95.7187 |
Formula
Percent error = |measured − true| ÷ |true| × 100Worked example
Inputs — Measured value: 9.6; True value: 9.81.
Results — Percent error = 2.1407 %; Absolute error = 0.21; Signed relative error = -2.1407 %.
Frequently asked questions
Why use absolute value?
Percent error usually ignores direction; the signed error shows over- or under-estimation.
What is a good percent error?
Depends on the experiment; under 5% is often acceptable in school labs.
What formula does the Percent Error Calculator use?
Percent error = |measured − true| ÷ |true| × 100.