Experimental data & uncertainty · SL/HL
Percentage Uncertainty Calculator
Enter a non-zero measured value and its absolute ± uncertainty.
Your values
Start with the example or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or input upload.
Result & working
ExampleThe calculator is loading. The worked example is also shown below.
Step-by-step working
The formula
percentage uncertainty = absolute uncertainty/|measured value| × 100%
| Symbol | Meaning |
|---|---|
| absolute uncertainty | The ± range associated with the measurement. |
When to use this calculator
State uncertainties to a sensible precision and keep the value to the same decimal place as its absolute uncertainty.
Worked example
The page opens with these example values. The result below is pre-generated for reference.
- percentage uncertainty = Δx/|x| × 100
- = 0.5/|25| × 100 = 2%
25 ± 0.5 mm
Common mistakes
- Do not confuse SD/SE from repeated data with instrument resolution unless the context justifies it.