The following standards, references, and guides published by various standards organizations provide “official” information about SI, the International System of Units.
To order copies of these publications, use the links provided herein; these publications are not available directly from USMA unless otherwise noted. Prices are, of course, subject to change; visit the vendors for current prices. To discover the meaning of any unrecognized acronyms, try USMA’s glossary of metric acronyms.
SI Brochure, 8th edition, 2006 —
The International System of Units (SI), aka Le Système international d’unités (SI)
“Since 1970, the Bureau International des Poids et Mesures, the BIPM (known in English as the International Bureau of Weights and Measures), has published seven previous editions of this document. Its main purpose is to define and promote the SI, which has been used around the world as the preferred language of science and technology since its adoption in 1948 through a Resolution of the 9th Conférence Générale des Poids et Mesures, the CGPM (known in English as the General Conference on Weights and Measures).”
This standard is available from BIPM, which has free downloadable copies of the full, 186-page French and English version; the 88-page English half; a 4-page concise summary; and a foldable pocket version; as well as a version for browsing online.
NIST SP 330 —
The International System of Units (SI)
NIST Special Publication 330 is the U.S. edition of the SI Brochure (above). It contains the English version of the BIPM’s SI Brochure with American spellings and some added “editors’ notes.”
The 97-page 2008 edition, equivalent to the current (8th) edition of the SI Brochure, is available free as a PDF download from NIST.
NIST SP 811 —
Guide for the Use of the International System of Units (SI)
NIST Special Publication 811 is an SI usage and style guide. Oriented toward scientific and technical writing, many of its rules are more detailed and strict than are typically used in everyday writing, but it is a valuable resource for determining correct usage.
In addition to much more in-depth coverage of topics than most of the other references mentioned on this page, SP 811 includes a comprehensive table of conversion factors, a section on rounding, a bibliography of other references, and a checklist for reviewing manuscripts, among other things.
The 89-page 2008 edition is available as a PDF download from NIST.
IEEE/ASTM SI 10-2010 —
American National Standard for Metric Practice
A 78-page standard from IEEE, ASTM International, and ANSI.
Abstract: “Guidance for the use of the modern metric system is given. Known as the International System of Units (abbreviated SI), the system is the basis for worldwide standardization of measurement units. Information is included on SI, a list of units recognized for use with SI, and a list of conversion factors, together with general guidance on proper style and usage.”
NIST SP 1038 —
The International System of Units (SI) — Conversion Factors for General Use
The main feature of NIST Special Publication 1038 is an 8-page table of unit conversion factors with usage notes, but this publication also provides a summary of SI units, prefixes, symbols, and usage, as well as an explanation of how to round converted values. SP 1038 provides a reasonably concise reference for readers who don’t need the excruciating detail of SP 811.
The 27-page 2006 edition is available as a PDF download from NIST.
Guide to the Use of the Metric System
An easy-to-use metric system style guide that shows the metric units and symbols and how to use them correctly. Also a very useful reference for teachers. This 34-page guide is available from USMA — see the table of contents and ordering information.
The USMA also provides other metric supplies and training aids.
There are, of course, many other SI standards and related publications that are more specialized or expensive, but can nevertheless be worth knowing about.