System International (SI)

metric conventions for SI use
and fundamental constants


Based on a 1875 treaty establishing an effort to develop a common set of measurement units to be used world wide, the metric system evolved in 1960 into the Système International d'Unités.  The American Institute of Physics publishes annually a guide for using SI units correctly.

Download the Guide to correct use of SI units. (pdf format)

Like most equations, the formulae used to understand the world generally have constants.   The Task Group on Fundamental Physical Constants of the International Council of Science periodically updates a self-consistent set of the best measurements of these constants.  The American Institute of Physics publishes annually this list.

Download the latest list of Fundamental Physical Constants. (pdf format)

Download a FREE pdf reader, Acrobat, from Adobe.   Acrobat


to ie-Physics menu
to Physics menu
to Physical Science menu

linked 8/10/2001
revised 1/20/2003
by D Trapp
Mac made