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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


Navigate to more SI base unit information:

Created March 25, 2021, Updated September 20, 2023