Uncertainty & measurement
Instrument Resolution & Zero Error Calculator
Choose the uncertainty convention given by your task or apparatus. Resolution alone does not establish instrument accuracy.
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
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Step-by-step working
The formula
Corrected value = observed value − signed zero offset
Δx = N_readings × Δreading + Δzero
| Symbol | Meaning |
|---|---|
| Zero offset | What the instrument reads when it should read zero. For a two-reading difference, enter the net offset (often zero). |
| Δreading | Half/full resolution or the supplied absolute uncertainty. |
| Δzero | Uncertainty in the applied correction, zero if treated as exact. |
When to use this calculator
A positive zero offset is subtracted; a negative offset is also subtracted and therefore increases the corrected reading. For a length obtained by subtracting two scale readings, enter the observed difference and choose two readings.
Half a division is a common starting convention for an analogue scale. A digital display may be assigned one last digit, half a step, or a manufacturer specification. Follow the actual task; neither choice is a universal IB requirement.
Two readings can share a calibration offset that cancels in their difference. The displayed addition rule is a conservative convention for the uncertainty components you supply; do not count a cancelled offset again.
Worked example
The calculator opens with these example values. All steps below are available even with JavaScript disabled.
- Corrected value = 12.4 − (0.2) = 12.2 mm.
- Reading uncertainty under the selected half convention = 0.05 mm.
- Absolute uncertainties add: 1 × 0.05 + 0.05 = 0.1 mm.
- Rounded result: (12.2 ± 0.1) mm.
(12.2 ± 0.1) mm
Common mistakes
- Do not confuse resolution, precision and accuracy.
- Subtract the signed zero error, not its magnitude.
- An offset correction does not eliminate uncertainty in the correction itself.