Every unit of length has a corresponding unit of area, namely the area of a square with the given side length. Thus areas can be measured in square metres (m2), square centimetres (cm2), square millimetres (mm2), square kilometres (km2), square feet (ft2), square yards (yd2), square miles (mi2), and so forth. Algebraically, these units can be thought of as the squares of the corresponding length units.

The SI unit of area is the square metre, which is considered an SI derived unit.

Converter of Area Unit

Units of Surface Area
Convert From
Rounded to decimals
Square Meter (m2)
Square Millimeter (mm2)
Square Centimeter (cm2)
Square Decimeter (dm2)
Square Dekameter (dam2)
Square Hectometer (ha2)
Square Kilometer (gal/s2)
Square Inch (in2)
Square Foot (ft2)
Square Yard (yd2)
Square Mile (mile2)
Acre (acre)
Are (are)
Hectares (ha)
Section (section)
Township (township)
Cent (ct)


Calculation of the area of a square whose length and width are 1 metre would be:

1 metre x 1 metre = 1 m2

and therefore, another square with different sides can be calculated as:

3 metres x 2 metres = 6 m2. This is, however, equivalent to 6 million millimetres square. Following this,

  • 1 kilometre square = 1,000,000 metres square
  • 1 metre square= 10,000 centimetres square = 1,000,000 millimetres square
  • 1 centimetre square = 100 millimetres square

Non-Metric units

In non-metric units, the conversion between two square units is the square of the conversion between the corresponding length units.

1 foot = 12 inches,

the relationship between square feet and square inches is

1 square foot = 144 square inches,

where 144 = 122 = 12 × 12. Similarly:

  • 1 square yard = 9 square feet
  • 1 square mile = 3,097,600 square yards = 27,878,400 square feet

In addition, conversion factors include:

  • 1 square inch = 6.4516 square centimetres
  • 1 square foot = 0.09290304 square metres
  • 1 square yard = 0.83612736 square metres
  • 1 square mile = 2.589988110336 square kilometres

Other Units Including Historical

There are several other common units for area. The “Are” was the original unit of area in the metric system, with;

1 are = 100 square metres

Though the are has fallen out of use, the hectare is still commonly used to measure land:

1 hectare = 100 ares = 10,000 square metres = 0.01 square kilometres

Other uncommon metric units of area include the tetrad, the hectad, and the myriad.

The acre is also commonly used to measure land areas, where

1 acre = 4,840 square yards = 43,560 square feet.

An acre is approximately 40% of a hectare.

On the atomic scale, area is measured in units of barns, such that:

1 barn = 10−28 square meters.

The barn is commonly used in describing the cross sectional area of interaction in nuclear physics.

In India,

  • 20 Dhurki = 1 Dhur
  • 20 Dhur = 1 Khatha
  • 20 Khata = 1 Bigha
  • 32 Khata = 1 Acre

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