The Task Group on Fundamental Constants is one of the original Task Groups of CODATA and was established in 1969. The purpose of the CODATA Task Group on Fundamental Constants is "to periodically provide the scientific and technological communities with a self-consistent set of internationally recommended values of the basic constants and conversion factors of physics and chemistry based on all of the relevant data available at a given point in time."

For more general information about CODATA please visit the following URL:

For more administrative information on the CODATA Task Group on Fundamental Constants please visit the following URL:

The primary output of the Task Group on Fundamental Constants is the multivariate least squares adjustment (LSA) of the values of the fundamental constants of nature. At the present time we are intending to produce a new LSA on a four year cycle. Each cycle includes all experimental data that are published or accepted by the Task Group by December 31 of that year. The most recent adjustment was completed in March 2007 with data accepted up to December 31, 2006 and it is known as the 2006 LSA. The values and uncertainties of the 2006 LSA of the fundamental constants may be found at:

Also available on this URL are a downloadable pdf copy of the 2006 LSA () published in Reviews of Modern Physics and J. Phys. Chem. Ref. Data, background information related to fundamental constants, an extensive bibliography of publications pertaining to fundamental constants, and links to other related sources of information.

Enquires about the Task Group on Fundamental Constants can be addressed to: Dr Barry M. Wood Institute for National Measurement Standards National Research Council Bldg. M-36, Rm. 1120 Montreal Rd. Ottawa K1A OR6 CANADA Telephone: +1 613 990 9225 Fax: +1 613 952 1394 Email: