# Area

### Learn more about Area

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

**Area** is a physical quantity expressing the size of a part of a surface. The term can also be used in a non-mathematical context to be mean "vicinity".

**Surface area** is the summation of the areas of the exposed sides of an object.

## Contents |

## [edit] Mathematical Usage

### [edit] 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 (fahomia in some sources
^{[citation needed]}) = 3.34450944 square metres - cadastral moon(acre) = 1600? square fathoms = 5755 square metres
^{[citation needed]}

### [edit] Useful formula

Common equations for area: | ||
---|---|---|

Shape | Equation | Variables |

Rectangle | <math>l \cdot w \,</math> | <math>l</math> and <math>w</math> are the lengths of the rectangles sides (length and width). |

Triangle | <math>\frac{1}{2}b \cdot h \,</math> | <math>b</math> and <math>h</math> are the base and altitude (height), respectively. |

Disk* or Circle | <math>\pi \cdot r^2 \,</math> | r is the radius. |

Ellipse | <math>\pi \cdot a \cdot b \,</math> | <math>a</math> and <math>b</math> are the semi-major and semi-minor axis. |

Sphere, Circular area | <math>4 \pi r^2 \,</math>, or <math>\pi d^2 \,</math> | <math>r</math> is the radius and <math>d</math> the diameter. |

Trapezoid | <math>\frac{1}{2}(a+b)h \,</math> | <math>a</math> and <math>b</math> are the parallel sides and <math>h</math> the distance (height) between the parallels. |

Cylinder | <math>2 \pi r (h + r) \,</math> | <math>r</math> and <math>h</math> are the radius and height, respectively. |

Lateral surface area of a cylinder | <math>2 \pi r h \,</math> | <math>r</math> and <math>h</math> are the radius and height, respectively. |

Cone | <math>\pi r (l + r) \,</math> | <math>r</math> and <math>l</math> are the radius and slant height, respectively. |

Lateral surface area of a cone | <math>\pi r l \,</math> | <math>r</math> and <math>l</math> are the radius and slant height, respectively. |

Circular sector | <math>\frac{1}{2} r^2 \theta \,</math> | <math>r</math> and <math>\theta</math> are the radius and angle (in radians), respectively. |

* A disk is the area enclosed in a circle. Often such area is called *cross-sectional area* like a cable or wire.

## [edit] See also

- Volume
- Orders of magnitude (area) — A list of areas by size.

## [edit] External links

- Area Conversion
- FORTRAN code for finding areas of various shapes
- Conversion cable diameter to circle cross-sectional area and vice versaaf:Oppervlakte

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