Uncertainty & measurement
Absolute uncertainty
Convert a percentage uncertainty to an absolute uncertainty.
Your measurements
Number formats & units
Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.
Calculated locally. No account or uploads.
Result & working
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Interpretation & assumptions
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Formula & example
The relationship
What the variables mean
| Symbol | Meaning |
|---|---|
| Measured value. | |
| Percentage uncertainty entered as a percentage, for example 2 for 2%. | |
| Absolute uncertainty in the unit of x. |
Worked example
- Measured value x
- 4.52
- Percentage uncertainty (%)
- 0.664
- Result unit (optional)
- V
- Uncertainty significant figures
- 1 significant figure
0.0300128 V
Follow the example steps
- Absolute uncertainty Δx = |x| × p / 100
- = |4.52| × 0.664 / 100 = 0.0300128 V
- Rounded measurement: (4.52 ± 0.03) V
Common mistakes
Enter a percentage as a percentage, not a decimal fraction.
Incorrect approach
x = 50, 2%: Δx = 50 × 0.02/100 = 0.01
Correct approach
Δx = 50 × 2/100 = 1
More checks before you submit
- 2% is entered as 2, not 0.02.
- The ± uncertainty is non-negative even if the measured value is negative.
- A displayed result should have the same decimal place as its rounded uncertainty.
Method notes
Use this when a specification or an earlier propagation calculation supplies relative uncertainty, but your report needs x ± Δx.
This conversion does not decide the original uncertainty. Instrument resolution, calibration and repeated measurements must be evaluated separately. For a zero reading, specify an absolute uncertainty directly.