The impact on calibration services of the SI redefinition
In November 2018, at the General Conference on Weights and Measures, from May 2019, all the base units will be defined in terms of defining constants, which are the most stable things available for us to use.
The new definitions impact four of the base units: the kilogram, ampere, kelvin and mole. The most substantial change will be to how mass is disseminated within national measurement institutes (NMIs). The kilogram will defined in terms of the Planck constant rather than via the International Prototype of the Kilogram held at the International Bureau of Weights and Measures in France.