Accredited laboratories are required to determine the Calibration Measurement Capabilities (CMC) which represented a 95% probability (k=2) that a published measured value would be correct. In the past the CMC was posted to a certificate of calibration. Later, labs were required to calculate Measurement Uncertainties. MU’s are now posted to a certificate. MU’s are always larger than CMC’s. because MU’s are a combination of the lab’s CMC and uncertainties at the time of calibration. The MU is used to calculate the measurement TUR. Read our position on TUR’s and statements of compliance on certificates issued.