U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Physical Measurement Laboratory

NIST Guide to the SI, Version History

Share

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)
Metrology
Created February 2, 2016, Updated July 18, 2019