Standard Article


  1. Bernd R. L. Siebert,
  2. Jörn Stenger

Published Online: 15 MAR 2011

DOI: 10.1002/3527600434.eap552.pub2

Encyclopedia of Applied Physics

Encyclopedia of Applied Physics

How to Cite

Siebert, B. R. L. and Stenger, J. 2011. Units. Encyclopedia of Applied Physics. 7–32.

Author Information

  1. Physikalisch-Technische Bundesanstalt, Braunschweig, Germany

Publication History

  1. Published Online: 15 MAR 2011


A generally accepted consistent system of dimensions and units is indispensable for trade, industrial production, communication in pure and applied science, and many other applications. Requirements on a system of units for expressing the values of quantities are presented and discussed. The International System of Units (SI), based on its recent eighth edition by the Bureau International des Poids et Measures (BIPM), is presented as such a consistent system of units. Guidance on its use is given and its future development is discussed. Support for converting non-SI units to SI units is provided in an appendix.


  • SI units