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Interpretation of the International System of Units for the United States

The Metric Act of 1866 says, “The metric system of measurement shall be defined as the International System of Units as established in 1960, and subsequently maintained, by the General Conference of Weights and Measures, and as interpreted or modified for the United States by the Secretary of Commerce.”

That interpretation is provided by the National Institute of Standards and Technology (NIST), the agency designated by the Department of Commerce with that responsibility.

The interpretation

The most recent interpretation was published in the Federal Register on 16 May 2008 (73 FR 28432). It announces that two NIST Special Publications serve as the U.S. interpretation of SI, and refers the reader to them: the 2008 editions of

Copies of the NIST publications are available from NIST. The Federal Register notice is available here.

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Updated: 2008-05-19