Calibration and Measurement Capability (CMC)

Calibration and Measurement Capability (CMC) represents the best measurement uncertainty a laboratory can deliver for a specific type of calibration under normal operating conditions. It is the uncertainty that appears on the laboratory's scope of accreditation and serves as the benchmark for the laboratory's measurement quality. CMC values are validated during the accreditation assessment process and are publicly available on the accreditation body's website.

CMC is determined by evaluating the uncertainty budget for each measurement capability under near-ideal conditions — meaning the unit under test contributes minimally to the uncertainty. The CMC therefore reflects the inherent capability of the laboratory's standards, methods, environment, and personnel. When calibrating real instruments (which are not ideal), the actual reported uncertainty will typically be larger than the CMC because the unit under test contributes additional uncertainty through its own repeatability, resolution, and other characteristics.

For calibration management, CMC is important for evaluating and comparing calibration service providers. When selecting a laboratory for a calibration, the CMC should be compared to the required TUR to ensure the lab can provide sufficient measurement quality. If the CMC results in a TUR less than 4:1 for the specific tolerance being evaluated, guard-banding or alternative approaches must be considered. CMC values are also used in interlaboratory comparisons and for evaluating whether a laboratory's capabilities meet customer needs.