How to read a scope of accreditation before you buy a calibration

An ISO/IEC 17025 accreditation logo on a website tells you a laboratory is accredited for something. Whether it is accredited for YOUR measurement lives in a different document: the scope of accreditation, published by the accreditation body for every accredited lab.

Read the scope like a menu, not a diploma. Find the measured quantity, the range that covers your instrument, and the calibration and measurement capability (CMC) — the smallest uncertainty the lab may claim for near-ideal devices under routine conditions. If your 100 mm gauge block needs 0.1 µm and the scope line says 0.5 µm, that lab cannot serve that need with an accredited result, however good its marketing. Check, too, that the accreditation body belongs to the ILAC Mutual Recognition Arrangement, which is what makes the certificate portable across borders and auditors.

When the certificate arrives, ISO/IEC 17025 §7.8 sets what it must contain: identification of the items and standards used, the results with units, the expanded uncertainty with its coverage information, and — if any pass/fail statement appears — the decision rule applied. A 'certificate of calibration' with no uncertainty, no traceability statement and no accreditation symbol is a receipt, not evidence. The red flags are consistent: prices quoted per certificate rather than per measurement need, reluctance to share the scope line that covers your work, and conformity statements with no stated decision rule.