Survey Tolerance Checker
Compares a measured value against its design value and tolerance, reporting whether it passes or fails.
Inputs
Measured minus reference against your inclusive tolerance band, decided on the unrounded residual.
Enter the values and press Calculate.
Or load an example to see a worked result.
Batch inspection from CSV
Header row with columns such as label, measured, reference, tolerance and optionally lower, uncertainty, spec. A row without a reference or tolerance is counted as unassessed, never as a pass. Up to 10,000 rows; nothing is uploaded.
How the method works
Fixed example values for illustration — not your result.
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the measured value and the design or reference value, in the same unit.
- Choose a symmetric ± tolerance or separate lower and upper limits, taken from your project specification.
- Optionally add the measurement uncertainty, then read the residual, pass/fail, utilisation and margin.
- Each value has its own unit (m, mm, cm, ft or in) and is converted exactly before the decision. Add a point label and your specification reference, then use Batch inspection from CSV to check many rows at once: the summary counts passed, failed and unassessed rows separately and the CSV export keeps the raw residual and your reference.
How it works
Residual = measured − reference, worked out in exact decimal arithmetic so a value exactly on a limit is not tipped over it by binary rounding. The check passes when lower ≤ residual ≤ upper — both limits inclusive.
Utilisation = |residual| ÷ the limit on the side the residual falls. With a zero limit on that side it is undefined, and the values must match exactly.
With an uncertainty U the tool shows the interval residual ± U and whether it sits inside, outside or across the band. It does not invent a decision rule for the straddling case — apply your project's.
Worked example
100.045 vs 100.000, ±0.05. Residual +0.045, within tolerance at 90% utilisation with 0.005 to spare. Exactly +0.05 still passes; +0.050001 fails before any display rounding.
Common mistakes
- Rounding the measurement before checking it — the decision uses the unrounded residual.
- Mixing units between the measurement and the tolerance.
- Treating an interval that straddles a limit as a pass.
Frequently asked questions
Does it work for any unit?
Yes — use the same unit for the measured value, the reference value and the tolerance.
Where does the tolerance come from?
From your project specification or contract. The tool applies the number you enter; it does not assume a standard.
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Cite this tool
Zerdly. (2026). Survey Tolerance Checker. Retrieved from https://www.zerdly.com/tools/survey-tolerance-checker/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.