The NIST Reference on Constants, Units and Uncertainty
Constants,
Units &
Uncertainty
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Version history

These are the 2010 CODATA recommended values of the fundamental physical constants, the latest CODATA values available. For additional information, see Background information related to the constants.

Citation example:
P.J. Mohr, B.N. Taylor, and D.B. Newell (2011), "The 2010 CODATA Recommended Values of the Fundamental Physical Constants" (Web Version 6.0). This database was developed by J. Baker, M. Douma, and S. Kotochigova. Available: http://physics.nist.gov/constants [Friday, 22-Jul-2011 10:04:27 EDT]. National Institute of Standards and Technology, Gaithersburg, MD 20899.

Version 6.3
23 April 2012
A preprint of the paper "CODATA Recommended Values of the Fundamental Physical Constants: 2010," by P.J. Mohr, B.N. Taylor, and D.B. Newell, giving the details of the adjustment of the constants has been added to the website. [1.2 MB PDF]
Version 6.2
30 June 2011
The correlation coefficients were updated to the 2010 CODATA values.
Version 6.1
22 June 2011
Some of the numbers in the table of ascii values were corrected and the relative uncertainty of the electron-helion mass ratio was added to the relevant PDF and gif files.
Version 6.0
2 June 2011
Values updated to the 2010 CODATA recommended values. The 2010 values replace the previously recommended 2006 CODATA values, which are available in archived tables.
Version 5.2
28 June 2008
A reprint of the paper "CODATA Recommended Values of the Fundamental Physical Constants: 2006," by P.J. Mohr, B.N. Taylor, and D.B. Newell, giving the details of the adjustment of the constants has been added to the website. It was published in the Reviews of Modern Physics 80, 633 (2008).
Version 5.1
31 December 2007
A preprint of the paper CODATA Recommended Values of the Fundamental Physical Constants: 2006, by P.J. Mohr, B.N. Taylor, and D.B. Newell, giving the details of the adjustment of the constants had been added to the website.
Version 5.0
7 March 2007
Values updated to the 2006 CODATA recommended values. The 2006 values replace the previously recommended 2002 CODATA values, which are available in archived tables.
Version 4.2
24 May 2005
Various files were updated to reflect the publication date of the Reviews of Modern Physics article. The correlation coefficients have been updated to give better accuracy. The file of residuals Y has been corrected.
Version 4.1
18 April 2005
Numerical data associated with the 2002 least-squares adjustment of the values of the constants is provided in this version with enough significant figures to be useful in related calculations. The notation is that given in Reviews of Modern Physics 72, 351 (2000), Appendix E. The data is from the CODATA 2002 least-squares adjustment described in Reviews of Modern Physics 77, 1 (2005).
Version 4.0
9 December 2003
Values updated to the 2002 CODATA recommended values. A table of all constants in ascii is available in this version. The 2002 values replace the previously recommended 1998 CODATA values, which are available in archived tables.
Version 3.2
1 October 2003
The pages giving the conversion from hartree to joule and their correlation coefficient were corrected to give the appropriate values of the standard and relative standard uncertainties instead of the previously listed "(exact)" statements.
Version 3.1
3 December 1999
Various minor changes from Version 3.0 have been made, including the following. The last digit of each of three values related to the Rydberg constant has been changed by 1, the convention of giving values of properties of the negatively charged muon and tau has been adopted, and the symbol for the molar mass constant has been changed. Further details are available.
Version 3.0
23 July 1999
Values updated to the 1998 CODATA recommended values. Correlation coefficients available between all constants. The 1998 values replace the previously recommended 1986 CODATA values, which are available in an archived document.
Version 2.1
21 May 1998
Search algorithm improved to exclude prepositions. Links to selected scientific data added.
NOTE: Between July 6, 1998 and August 13, 1998, the search engine inadvertently returned very preliminary working values intended for the next CODATA set of recommended values. Since these were not the final values for that update, they should be completely ignored. During that period, the category tables provided the correct 1986 CODATA values.
Version 2.0
17 February 1998
Entirely new interface, as part of the "NIST Reference on Constants, Units, and Uncertainty." Search interface introduced. Values are available individually in tables (from which users may copy the numbers), or by category in both graphical and pdf formats.
Version 1.3
1 October 1996
Most mathematical expressions have been converted from graphic images to html notation for faster access.
Version 1.2
11 September 1996
Postscript and Acrobat versions have been made available.
Version 1.1
17 July 1996
Graphic images of the tables of constants have been improved.
Version 1.0
6 October 1994
The 1986 recommended values are first made available on the internet.

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