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SI Units – Area

SI Units area banner
Credit: NIST
Pixabay, Aerial view of farmland
Credit: Pixabay, Aerial view of farmland

Area is the amount of surface a two-dimensional shape can cover, measured in square units. The SI unit of area is the square meter (m2), which is a derived unit.

Common Units of Area

100 square millimeters (mm2)

= 1 square centimeter (cm2)

100 cm2

= 1 square decimeter (dm2)

100 dm2

= 1 square meter (m2)

100 m2

= 1 square dekameter (dam2) = 1 are

100 dam2

= 1 square hectometer (hm2) = 1 hectare (ha)

100 hm2

= 1 square kilometer (km2)

Image of USPS Forever Postage Stamp
Credit: U.S. Postal Service, U.S. Flag Forever Stamp (2019)
  • Square millimeter (mm2) can be visualized as a square that is 1 mm on each side (or 1 mm x 1 mm).
  • Square centimeter (cm2) can be visualized as a square that is 1 cm on each side (or 1 cm x 1 cm).
  • Square meter (m2) can be visualized as a square that is 1 m on each side (or 1 m x 1 m). Square meters are used in intermediate applications, such as calculating the area of a room to purchase the right amount of carpet.
  • Hectare is a special name for 10,000 square meters (m2), which can be visualized as a square that is 100 m on each side (or 100 m x 100 m). Larger areas within a city neighborhood or the size of a farm can be measured in hectares (ha).
  • Square kilometer (km2) can be visualized as a square that is 1 km on each side (or 1 km x 1 km). Square kilometers typically measure very large areas.


Everyday Areas

550 mm2
(25 mm x 22 mm)

First Class U.S. Postage Stamp

616 cm2
(22 cm x 28 cm)

Office Paper

1.8 m2
(2 m x 0.9 m)

External Residential Door

162 m2
(9 m x 18 m)

NCAA Volleyball Court

7.77 ha
(0.0777 km2)

Jefferson Memorial Park Landscape, Washington, District of Columbia

7 ha
(0.07 km2)

Lyndon Baines Johnson Memorial Grove Park, Washington, District of Columbia

Resources for Students and Teachers:

  • Metric Rainfall Calculation Activity and Rainfall Rates (US Geological Survey). How much water falls during a rain storm? Choose an area and a rainfall amount (mL) to determine the volume of water (L) that fell from the sky and was delivered onto that area. You'll be surprised about much rain really does fall during a rainstorm. A variety of common rainfall rates (mm per hour) are described.
  • SI Prefixes. In the metric system of measurement, designations of multiples and subdivision of any unit may be arrived at by combining with the name of the unit the prefixes. (NIST)
  • Calculate Area. Become familiar with methods used to calculate the area of common objects. (NIST)
  • SI Volume. Explore resources to become familiar with units used to measure volume, including the liter. (NIST)
  • SI Units Card Deck (SP 1297). This activity offers a fun way to enhance understanding of the International System of Units, including the defining constants, base units, derived units with special names, and prefixes. (NIST)
  • Top 10 Tips for Teaching the Metric System. (NIST)

Navigate to more SI base unit information:

Created March 25, 2021, Updated January 16, 2024