# Area

### From Wikipedia, the free encyclopedia.

*This article explains the meaning of area as a physical quantity. The article area (geometry) is more mathematical.*

**Area** is a quantity expressing the size of a region of space. **Surface area** refers to the summation of the areas of the exposed sides of an object.

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## Units

Units for measuring surface area include:

- square metre = SI derived unit
- are = 100 square metres
- hectare = 10,000 square metres
- square kilometre = 1,000,000 square metres
- square megametre = 10
^{12}square metres

Imperial units, as currently defined from the metre:

- square foot (plural square feet) = 0.09290304 square metres.
- square yard = 9 square feet = 0.83612736 square metres
- square perch = 30.25 square yards = 25.2928526 square metres
- acre = 160 square perches or 43,560 square feet = 4046.8564224 square metres
- square mile = 640 acres = 2.5899881103 square kilometres

Old European area units, still in used in some private matters (e.g. land sale advertisements)

- square fathom = 3.5967 square metres
- cadastral moon(acre) = 1600� square fathoms = 5755 square metres

The article Orders of magnitude links to lists of objects of comparable surface area.

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## Useful formulas

- Area of a rectangle (and, in particular, a square): length × width
- Area of a triangle: ½ × base × height
- Area of a disk: π × r²
- Area of an ellipse: π × a × b
- Area of a sphere: 4 × π × r² = π × d²
- Total surface area of a right circular cylinder: 2 × π × r × (h + r)
- Lateral surface area of a right circular cylinder: 2 × π × r × h
- Total surface area of a right circular cone: π × r × (l + r)
- Lateral surface area of a right circular cone: π × r × l

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