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# SI Base Units Relationships Poster (SP 1247)

## Share

As of August 16, 2023 the physics.nist.gov historic SI Units site has permanently retired. This page and complete Metric (SI) Program contains current SI information. Contact TheSI [at] nist.gov (TheSI[at]nist[dot]gov) with comments, questions or concerns.

 Keywords: SI, metric system, base unit, derived unit, kilogram, kelvin, meter, candela, second, ampere, mole, international Audience: Students, Parents, Educators, General Public, Technology Coordinators, Outreach Ambassadors Grade Level: 6 to Higher Education Subjects: STEM, mathematics, physical science, chemistry, engineering, physics, biology and life sciences

Credit: E. Tiesinga, K. Dill, D. Newell/NIST

### Summary

This colorful resource provides a printable SI unit diagram, which illustrates the relationships between the SI base units and derived units with special names. This chart may be printed on any paper size but is recommended to be size 215.9 mm x 279.4 mm (8.5 in x 11 in). This resource is an interactive method to engage students in learning about the relationships of SI units. The diagram is aligned with the BIPM SI Brochure, 9th edition and NIST SP 330, The International System of Units (SI), 2019 edition.

The traditional SI base unit symbols are shown within rectangle shapes, with the unit name shown above the corresponding rectangle. The derived units with special names are shown in circle shapes, with the unit symbol and name within the circle. An expression for the derived unit in terms of other units shown in parenthesis. Derived units without special names are not illustrated. In the diagram, the derivation of each derived unit is indicated by arrows that bring in units in the numerator (solid lines) and units in the denominator (broken lines), as appropriate. The unit "degree Celsius,'' which is equal in magnitude to the unit "kelvin," is used to express Celsius temperature t, defined by the quantity equation t = T - T0, where T0 = 273.15 K, the ice point. This equality is indicated in the diagram by the symbol K in the °C circle. The numerical value of a Celsius temperature t expressed in degrees Celsius is given by the equation below "CELSIUS TEMPERATURE.'' A difference or interval of temperature may be expressed in kelvins or in degrees Celsius.

### Learning Objectives

• Recognize SI units of measure
• Observe SI unit relationships
• Develop SI unit familiarity

### Materials

• Required
• Digital file
• Paper
• Printer
• Recommended
• 215.9 mm x 279.4 mm (8.5 in x 11 in) size paper

### Safety

Use caution when handling paper edges to prevent injury.

### Teaching Tips

Explain the SI base units, unit definitions, and metric prefixes. State each base unit depends upon a defining constant. Additionally, mention the combination of SI base units creates the SI derived units. Hardcopy charts are available while supplies last. Contact the NIST Metric Program at TheSI [at] nist.gov (TheSI[at]nist[dot]gov) and include your name and U.S. mailing address. Use when playing game activities, described in the SI Base Units Card Deck (SP 1297).

## Contacts

• Metric Program
Created July 13, 2022, Updated February 13, 2024