How to Define the Units of the Revised SI Starting from Seven Constants with Fixed Numerical Values.

Abstract

As part of a revision to the International System of Units (SI) approved in 2018 and to take effect in May 2019, the seven base units will be defined by giving fixed numerical values to seven defining constants. This article shows how the definitions of all seven base units can be derived efficiently from the defining constants, with the result appearing as a table. The table's form makes evident a number of connections between the defining constants and the base units. Appendices show how the same methodology could have been used to define the same base units in the present SI, as well as the mathematics that underpins the methodology. Since the base units are now defined in terms of constants, then all units in the SI are now defined in terms of those constants.