Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

NIST Guide to the SI, Version History

Example of how to reference SP 811 (2008 edition) of this online document (Replace year, month day with database access date.):
Ambler Thompson and Barry N. Taylor (2008), Guide for the Use of the International System of Units (SI) NIST Special Publication 811, 2008 Edition (version 3.2). [Online] Available: http://physics.nist.gov/SP811 [year, month day]. National Institute of Standards and Technology, Gaithersburg, MD.

Optional addition:
Originally published as Guide for the Use of the International System of Units (SI), NIST Special Publication 811, U.S. Government Printing Office, Washington, DC (2008 Edition).
 
Citation Form:
Author/editor (Year), Title (edition). [Type of medium] Available: URL [Access date].
Web Version 3.2
July 2008
 
HTML (2008 edition) online
Web Version 3.1
June 2008
 
SP811 (1995 edition) taken offline
Web Version 3.0
May 2008
 
PDF (2008 edition) online.
Published Version
March 2008

 
Guide for the Use of the International System of Units (SI), NIST Special Publication 811, U.S. Government Printing Office, Washington, DC (2008 Edition, 1st printing - supersedes 1995 Version)
Version 2.3
May 2007
 
Greek letters were converted from images to HTML code in the text. Equations remain displayed as images.
Version 2.2
March 2004
 
Footnote 28 was added for "acceleration of free fall, standard" in Sec. B.8 and Sec. B.9. The layout of the footnotes page was modified.
Version 2.1
April 2001
 
Added navigation to Appendix B8 and Appendix B9.
Version 2.0
July 2000
 
HTML version online.
Version 1.1
October 1996
 
Update of PDF version.
Version 1.0
May 1996
 
PDF version online.
Published Version
April 1995
Guide for the Use of the International System of Units (SI), NIST Special Publication 811, U.S. Government Printing Office, Washington, DC (1995 Edition, 2nd printing - supersedes September 1991 Version)
Created February 2, 2016, Updated July 18, 2019