Is your document a declaration of conformance or a calibration certificate?
Applies to: ISO 6789-1:2017, ISO 6789-2:2017 · Updated 2026-10-27
Technical review: Alston Hsiao (Chieh-Jen Hsiao), CTO, STAND
Check two things: does the document state whether the results fall within the permissible deviation, and whose uncertainty does it report? A document that states whether or not the results conform, with uncertainty information only for the measurement device, is a Part 1 declaration of conformance. A document reporting W and W′ for this tool at every calibration point is a Part 2 calibration certificate.
First identify the edition
Find the standard reference on the document. ISO 6789-1:2017 corresponds to a declaration of conformance; ISO 6789-2:2017 corresponds to a calibration certificate.
Start by looking for a part number. A reference to ISO 6789-1 or ISO 6789-2 identifies the 2017 edition, because the 2003 edition was not divided into parts. In practice, a reference to “ISO 6789” without a part number or year often means the 2003 edition or wording carried over from earlier documents, but you cannot assume that. The simplest approach is to ask the supplier to add the year. When ordering, also specify “ISO 6789:2003” or “ISO 6789-1:2017” in the order.
If the reference is ISO 6789:2003, the distinction explained here does not apply. See Can an ISO 6789:2003 report still be used, and how should it be read?.
Why serial numbers and measurement figures are not enough
Both documents identify the tool type and serial number, and both include measurement values. Neither “It has a serial number, so it is a calibration certificate” nor “It contains numbers, so the tool has been calibrated” is a reliable way to identify the document. The important differences are its conclusion and the subject of its uncertainty information.
| Item | Declaration of conformance (Part 1) | Calibration certificate (Part 2) |
|---|---|---|
| Tool identification | Tool type and serial number | Tool type and serial number |
| Measurement values | Observed values at each target torque | All values recorded during calibration, plus the mean at each calibration point |
| Conclusion | States whether observed values are within the permissible deviation | A pass/fail statement is not required |
| Uncertainty | Maximum error and uncertainty interval of the measurement device | W and W′ of this tool at each calibration point |
What does this mean for the documents you received?
- You received both: The supplier has provided two kinds of evidence. One states whether or not the tool conforms; the other reports its measurement results and the confidence associated with them.
- You received a calibration certificate but need a pass/fail answer: The certificate does not necessarily include a conformance decision. If you need that conclusion, agree on how the decision will be made with the calibration provider in advance.