New edition of metric-system guide published

We all know that in the movies, 'the fundamental things apply, as time goes by.' But in the real world, the fundamental things are continuously being updated, refined and redefined so the National Institute of Standards and Technology has published a new U.S. edition of the 'International System of Units' ' better known as the metric system.

NIST Special Publication 330 is the U.S. version of the English language text of the eighth edition Le Syst'me International d' Unit's (SI), the standard reference to the International System (SI) published by the International Bureau of Weights and Measures. The most recent U.S. edition was published in 2001. The revised guide includes changes made since 1998, including a new chapter on units for quantities describing biological effects, and symbols for expressing values for enzyme catalytic activity in biology and medicine.

The metric SI has never really caught on with U.S. consumers, who measure automobile performance in miles per gallon rather than kilometers per liter, but it is the common language of scientific and technological research. The U.S. Omnibus Trade and Competitiveness Act of 1988 and the America Competes Act of 2007 establish it as the 'preferred system of weights and measures for [U.S.] trade and commerce.'

The secretary of Commerce has the responsibility of interpreting the SI for the United States. The U.S. version standardizes the American spelling of some English words using the United States Government Printing Office Style Manual, which follows Webster's Third New International Dictionary rather than the Oxford Dictionary. The spellings 'meter,' 'liter,' and 'deka' are used rather than 'metre,' 'litre,' and 'deca.' And it is a 'metric ton' rather than 'tonne.' On the numerical side, the decimal marker used in this country is a dot or period, but in France it is a comma.

The new edition also establishes a new unit and symbol for the mol; the symbol 'kat' for katal, which expresses values of the quality of catalytic activity; and new units for describing biological effects. All recent decisions by international standards bodies that affect the SI are included.

NIST also has published a companion document, Special Publication 811 titled 'Guide for the Use of the International System of Units' to help authors with correct SI usage and unit conversion. It also includes an editorial checklist for reviewing manuscripts for conformity with the system.

About the Author

William Jackson is a Maryland-based freelance writer.


  • business meeting (Monkey Business Images/

    Civic tech volunteers help states with legacy systems

    As COVID-19 exposed vulnerabilities in state and local government IT systems, the newly formed U.S. Digital Response stepped in to help. Its successes offer insight into existing barriers and the future of the civic tech movement.

  • data analytics (

    More visible data helps drive DOD decision-making

    CDOs in the Defense Department are opening up their data to take advantage of artificial intelligence and machine learning tools that help surface insights and improve decision-making.

Stay Connected