CODATA Membership


Task Groups

Working Groups







International Council for Science : Committee on Data for Science and Technology
CODATA The Committee on Data for Science and Technology
< home > < newsletter > < discussion list > < data science journal > < contact > < members area >

Fundamental Physical Constants
established in 1969

Approved by the CODATA 23rd General Assembly in Montréal 2002
Renewal approved by the CODATA General Assembly, Berlin 2004
Renewal approved by the CODATA 25th General Assembly, Beijing 2006
Renewal approved by the CODATA 26th General Assembly, Kyiv 2008
Renewal approved by the CODATA 27th General Assembly, Cape Town 2010
Renewal approved by the CODATA 28th General Assembly, Taipei 2012

Objectives of Task Group

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.



Dr. David Newell
Bldg. 220, Rm. B158
100 Bureau Drive, Stop 8171 Gaithersburg, MD 20899
Telephone: + 1 301 975 4228
Fax: + 1 301 975 2115


Dr. Barry M. Wood
Institute for National Measurement Standards
National Research Council
Bldg. M-36, Rm. 1120
Montreal Rd.
Ottawa K1A OR6
Telephone: +1 613 990 9225
Fax: +1 613 952 1394


Dr. Franco Cabiati
Istituto Nazionale di Ricerca Metrologica
Strada delle Cacce 91
I-10135 Torino
Telephone: +39 011 3919 435
Fax: +39 011 346384

Dr. Joachim Fischer
Physikalisch-Technische Bundesanstalt
Abbestrasse 2-12
10587 Berlin, Germany
Telephone: +49 30 3481 7473
Fax: +49 30 3481 7508

Dr. Jeff Flowers
Center for Basic, Thermal and Length Metrology
Building 1, Room 102
Queens Road
Teddington, Middlesex TW11 OLW
Telephone: +44 20 8943 6671
Fax: +44 20 89436939

Dr. Kenichi Fujii
National Metrology Institute of Japan
AIST Tsukuba Central 3
1-1-1 Umezono, Tsukuba
Ibaraki 305-8563
Telephone: +81 298 61  4316
Fax: +81 298 50 1464

Dr. Savely G. Karshenboim
D. I. Mendeleyev Institute of Metrology
19 Moskovsky pr.
St. Petersburg 198005
Telephone: +7 812 3239675
Fax: +7 812 1130114

Dr. Peter J. Mohr
NIST, Bldg. 225, Rm. A261
100 Bureau Drive, Stop 8401
Gaithersburg, MD 20899-8420
Telephone: +1 301 975 3217
Fax: +1 301 990 1350

Dr. Francois Nez
Laboratoire Kastler-Brossel
UPMC case 74
tour 12, 1er etage
4 place Jussieu
F-75252 Paris CEDEX 05
Telephone: +33 1 44 27 72 48
Fax: +33 1 44 27 38 45

Prof. Krzysztof Pachucki
Institute of Theoretical Physics
University of Warsaw
Hoza 69, 00-681 Warsaw
Telephone: + 48 22 5532246
Fax: + 48 22 6219475

Dr. Terry J. Quinn CBE FRS
92 rue Brancas
92310 Sèvres
Telephone: +33 1 4623 0656

Dr. Barry N. Taylor
NIST, Bldg. 225, Rm. B161
100 Bureau Drive, Stop 8401
Gaithersburg, MD 20899-8401
Telephone: +1 301 975 4220
Fax: +1 301 975 4578

Prof. Zhang Zhonghua
Electricity and Quantum Division
National Institute of Metrology
No. 18, Bei San Huan Dong Lu
Beijing 100013
Telephone: +86 10 64297138
Fax: +86 10 64220525

BIPM Liaison

Dr. Claudine Thomas
Pavillon de Breteuil
F-92312 Sèvres Cedex
Tel.    +33 1 45 07 70 73
Fax    +33 1 45 07 62 62

CODATA Executive Committee Liaison

Dr. Gordon Wood
1800 Woodhaven Heights
Ottawa, Ontario, K1E 2W2
Telephone +1 613-824-3903

Recent Activities

Report as of 30th June 2011

The annual meetings of the Task Group were held 15 July 2006 in conjunction with the Conference of Precision Electromagnetic Measurements (CPEM) in Torino, Italy and on 14 June 2007 at the bureau international des poids et mesures (BIPM), Sèvres, France.  The primary activity of the task group is the ongoing survey of publications for new information relevant to the adjustment of the values of the constants and the analysis of that information to determine its influence on the values of the constants. Review of this work is the main subject of meetings of the Task Group. These meetings also focused on preparation for the 2006 adjustment and its accompanying publications, as well as discussions involving the proposed changes to the SI using fixed values of a set of fundamental constants.

The 2006 CODATA adjustment of the values of the fundamental constants was completed in March 2007 and the results were made available on the Web at  A brief summary article was published The fundamental physical constants  by P. J. Mohr, B. N. Taylor, and D. B. Newell , Phys. Today 60(7), 52-55 (2007).  A more detailed article is being prepared for submission to Reviews of Modern Physics.

Considering the link between SI units and fundamental constants and the critical role that fundamental constants are expected to play with regard to proposed changes to the SI, the task group requested to the International Conference on Weights and Measures (CIPM) to have CODATA made an official member of the Consultative Committee on Units (CCU).  This request was granted.  Drs Wood and Newell of the task group represented CODATA at the CCU meeting held at BIPM in Paris on 11-13 June 2007.

A number of the task group members have been involved in presentations and public discussions explaining different aspects of the role of fundamental constants in the proposed changes to the SI.  This included the round table discussion held at CPEM 2006 in Torino, Italy which has been published CPEM 2006 round table discussion 'Proposed changes to the SI', Michael Stock and Thomas J Witt, Metrologia 43 No 6 (December 2006) 583-587.  As well, a session about SI units was held at the NCSLI conference in St Paul in July 2007 including "Proposed Changes to The SI and Their Impact on Electrical Metrology ", B. Wood to be published in Measure in 2008.

As already mentioned, the results of the 2006 least-squares adjustment of the fundamental constants has been made available on the Web at

One paper summarizing this work has been published in Physics Today.

The task group has been active in promotion of the proposed changes to the SI and has represented CODATA at the 2006 CCU meeting considering this issue.

It is recognized that, because the fundamental physical constants of nature are the links in the chain that binds all of science and technology together, an internationally accepted set of recommended or ``best'' values of the constants and conversion factors for energy equivalents must be made available periodically for the use of the scientific and technical communities. Over the years, the CODATA recommended values have been widely accepted by the scientific and technical communities as the ``official'' values, thereby providing a consistency of the treatment of data that relies on the values of the constants.  It is important that the work of the Task Group continues in order to monitor the relevant research and data production and provide updates with new values of the constants when necessary.  CODATA is recognized as the authoritative body to recommended values of the fundamental physical constants, and it should continue to provide this service to the scientific and technical communities.  Further, the recommendations of the Task Group to the CCU have contributed to their recommendation to the CIPM that is likely to change the nature of the International System of Units in a significant way.  This change will also have the effect of making many of the fundamental constants significantly more accurate and in most cases, the energy conversion factors will become exact.

Beyond the 2006 recommended values, work is in progress on the next adjustment and production of recommended values of the constants and conversion factors for energy equivalents. The Task Group will monitor closely the new data that becomes available relevant to the fundamental constants and, when warranted, issue a new set of recommended values. 

It is anticipated that a new recommended set of constants will be issued on or before 2010.  This deadline may be altered to adapt to developments in the proposed changes to the SI.  It now seems universally accepted by all of the concerned groups that the task group’s recommended values will be used in this process.  This would mean that the task group’s impact is enormous and centred at the core of the redefinition of the world’s measurement system.

The task group will continue making new adjustments promptly and widely available, especially on the World Wide Web and has committed to preparing  a new set of recommended values no less than every four years and possibly as soon as two years after the issuance of the previous values, if justified by the newly available data.

The CODATA Task Group on Fundamental Constants has been in existence since 1969, almost 40 years! It is recognized internationally as the definitive body for periodically carrying out least-squares adjustments of the constants and issuing recommended values of the constants and conversion factors for energy equivalents for world-wide use.

Working to improve the quality, reliability, management and accessibility of Data for Science and Technology

| home | about | codata membership | resources | task and working groups |
| archives | newsletter | contact | members area |

| XML - CODATA RSS Feed | RSS Feed subscription instructions |