International Standards and Conformity Assessment for all electrical, electronic and related technologies
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SI Zone

International System of Units



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Giovanni Giorgi
Italian scientist and engineer

In October 1901, a very successful Italian scientist and engineer Giovanni Giorgi showed at the congress of the Associazione Elettrotecnica Italiana (A.E.I.) in Rome that a -coherent system of units- could be achieved by adding an electric unit to the three mechanical units (centimetre, gram, second) of the existing CGS system. The event can be considered as the birth of what is now known as the International System of Units, or SI.

The history surrounding the birth of the SI is an example of how the world of international standardization can truly deliver a solution that meets past, present and future market needs.

The birth of the SI is inseparably linked to the personality of Professor Giovanni Giorgi. This visionary Italian anticipated future needs and provided as early as 1901 not only suggestions for a coherent system of units, but a full-fledged solution. His case also shows that being ahead of one’s time can draw more criticism than being behind. But fortunately, Giovanni Giorgi had the satisfaction of witnessing how, after many years of seemingly endless debate, his original proposals were accepted without major changes.

This saga is, however, not merely of historical interest. We know that specific styles of art, literature, technology, etc., tend to be superseded by later ones. Here again, Giovanni Giorgi’s legacy is exceptional. Far from being challenged by any better system, the SI keeps proving its worth and is used day in and day out in science, technology, medicine, trade, and the society at large.


All historical information presented in these pages comes from the book: "1901-2001, Celebrating the Centenary of SI - Giovanni Giorgi's Contribution and the Role of SI", published in 2001 by the IEC for the 100th anniversary of the International System of Units.

Examples of units (covering Electricity and magnetism, Light) come from ISO's SI Guide.