A revised International System of Units (SI) is expected to be established by the
26th General Conference on Weights and Measures when it convenes in November 2018 and to
be put into practice starting on 20 May 2019, World Metrology Day. In consequence, the
article published in this journal in 2011, “The Current SI Seen from the Perspective of
the Proposed New SI,” is updated in this paper, which provides an opportunity to again
demonstrate the usefulness of the quantity calculus in dealing with quantities and
units. The quantity calculus and the seven defining constants of the current and revised
SI are reviewed, and expressions for the seven current and revised SI base units are
given. Relationships between the magnitudes of revised and current SI units and
expressions for the numerical values of current SI defining constants expressed in
revised SI units are also obtained using the quantity calculus.
The role of fundamental constants in the International System of Units (SI): present and future
