ISO 17025:2017 is the applicable standard for all non-medical testing and calibrations, including dimensional tests such as length. Depending on the country and accreditation body, the laboratory’s testing scope will fall under, for example, the Dimensional Testing program of the accreditation body for ISO 17025 accreditation. Note that because there are many ISO standards for packaging, including medical devices and other high-risk goods, the client laboratory is responsible for ensuring the specific requirements of standard test specifications are met.
Perhaps you do not need accredited tests for dimensions but just want assurance in verifying the measurements? In that case, testing accreditation may not be necessary, but the calibrated measuring devices used for testing must be suitable for use (e.g resolution, range and precision). The laboratory calibrating the devices should be accredited as an ISO 17025 calibration laboratory for dimension metrology (length) and provide ISO 17025 compliant calibration certificates.