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Physical Measurement Laboratory

Office of Weights and Measures

Measurement System Basics - SI and US Customary Units for Regulatory Officials

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Description and Purpose:

This 1.5-hour webinar will introduce the measurement systems commonly used in the United States, including the International System of Units (SI) and U.S. Customary systems (e.g., Avoirdupois, Apothecary, and Troy units).

This session is ideal for participants who would like to become more familiar with measurement systems used in field, laboratory, and manufacturing activities.  Accurately expressing measurement quantities in written communications is critical. Writing style best practices, unit symbols and prefixes usage, and error recognition will be addressed.

To promote collaboration among members of the same organization, for example teachers within the same U.S. school, grade, or subject, “Group” participation in a webinar session from a centralized facility location can be pre-arranged with the course Instructor, on a case-by-case basis. For more information, please contact thesi [at] nist.gov (TheSI[at]nist[dot]gov).

Course Info

At the end of this session, using your notes, you will be able to:

  • DEFINE the terms legal unit of measurement and legal metrology.
  • IDENTIFY systems of measurement units used in the United States.
  • LIST official sources of measurement system information. DISCOVER common unit symbol writing errors.

Weights and Measures field and program officials, state laboratory metrologists, and others who have responsibilities for conducting regulatory and enforcement activities.

General Info & Requirements

All requests for course attendance should be submitted via the OWM Contacts System. The OWM Training and Events calendar lists currently scheduled classes. Please see the Training FAQs or OWM Contacts System Help. For more information, email your questions to owm [at] nist.gov (owm[at]nist[dot]gov).

Successful completion includes participation in all activities and discussions. Session participants will receive a Certificate of Attendance (does not include participant name or CEUs) by email after the session. Attendance is recorded in the Training History tab, available in the OWM Contacts System.

The webinar will be a live stream, so participants must have a constant connection during the webinar (hard-wired is preferred). Review these system requirements to verify that MS Teams may be used on your computer, mobile device, or web browser. The performance of MS Teams may be influenced by other factors, such as network connectivity or other device applications.

Operating System (browsing) configurations:

  • Windows
    • Windows 8.1 and later, 64-bit;
      • Google Chrome;
      • Mozilla Firefox; and
      • Microsoft Edge.
  • macOS
    • One of the three latest MacOS versions;
      • Mozilla Firefox;
      • Apple Safari (no calls via Teams possible); and
      • Google Chrome.
  • Linux
    • Operating system: DEB or RPM;
    • Desktop environment: GNOME, KDE;
      • Mozilla Firefox; and
      • Opera.

Web Browsers:

  • On computers running Windows, Mac, or Linux, ensure you have the latest release of one of these browsers:
    • Google Chrome;
    • Mozilla Firefox;
    • Apple Safari; and
    • Microsoft Edge.
Metrology, Metric and Weights and measures

Contacts

Created August 19, 2025, Updated August 21, 2025
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