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Unit conversions
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Summary
SI base units
SI derived units
SI prefixes
SI brochure (8th edition)
Brief history of the SI
Linking SI base units to fundamental and atomic constants
Unit conversions
Direct access

Official values of conversion factors
  • can be found in the ISO Standards Handbook 31 – Quantities and units, which can be purchased from the usual ISO outlets;
  • may also be consulted on-line in Appendix B of NIST Special Publication 811 (PDF format).
  • The CODATA internationally recommended values for the fundamental physical constants are available from the NIST site.
    Several on-line unit conversion facilities exist, and links to a number of these are provided by the NIST. The BIPM has no plans to develop its own on-line conversion programs.