Uncertainty & measurement
Absolute Uncertainty Calculator
Turn a percentage uncertainty into an uncertainty with the same units as your measurement.
Your measurements
Start with the example, or enter your own values. Use a dot for decimals and e for scientific notation.
Calculated locally. No account or uploads.
Result & working
ExampleThe calculator is loading. You can read the worked example below.
Step-by-step working
The formula
Δx = |x| × p / 100
| Symbol | Meaning |
|---|---|
| x | Measured value. |
| p | Percentage uncertainty entered as a percentage, for example 2 for 2%. |
| Δx | Absolute uncertainty in the unit of x. |
When to use this calculator
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.
Worked example
The calculator opens with these example values. All steps below are available even with JavaScript disabled.
- Absolute uncertainty Δx = |x| × p / 100
- = |4.52| × 0.664 / 100 = 0.0300128 V
- Rounded measurement: (4.52 ± 0.03) V
0.0300128 V
Common mistakes
- 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.