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The **square metre** (International spelling as used by the International Bureau of Weights and Measures) or **square meter** (American spelling) is the SI derived unit of area with symbol **m ^{2}**.

The **International Bureau of Weights and Measures** is an intergovernmental organization that was established by the Metre Convention, through which member states act together on matters related to measurement science and measurement standards. The organisation is usually referred to by its French initialism, BIPM. The BIPM's headquarters is based at Sèvres, France. It has custody of the International Prototype of the Kilogram and houses the secretariat for this organization as well as hosting its formal meetings.

**SI derived units** are units of measurement derived from the seven base units specified by the International System of Units (SI). They are either dimensionless or can be expressed as a product of one or more of the base units, possibly scaled by an appropriate power of exponentiation.

**Area** is the quantity that expresses the extent of a two-dimensional figure or shape, or planar lamina, in the plane. Surface area is its analog on the two-dimensional surface of a three-dimensional object. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat. It is the two-dimensional analog of the length of a curve or the volume of a solid.

Adding and subtracting SI prefixes creates multiples and submultiples; however, as the unit is exponentiated, the quantities grow geometrically by the corresponding power of 10. For example, a kilometre is 10^{3} (a thousand) times the length of a metre, but a square kilometre is 10^{32} (10^{6}, a million) times the area of a square metre, and a cubic kilometre is 10^{33} (10^{9}, a billion) cubic metres.

In mathematics, a **power of 10** is any of the integer powers of the number ten; in other words, ten multiplied by itself a certain number of times. By definition, the number one is a power of ten. The first few non-negative powers of ten are:

The **kilometre** or **kilometer** is a unit of length in the metric system, equal to one thousand metres. It is now the measurement unit used officially for expressing distances between geographical places on land in most of the world; notable exceptions are the United States and the road network of the United Kingdom where the statute mile is the official unit used.

A **billion** is a number with two distinct definitions:

The square metre may be used with all SI prefixes used with the metre.

Multiplication | Name | Symbol | Multiplication | Name | Symbol | |
---|---|---|---|---|---|---|

10^{0} | square metre (centiare) | m^{2} | 10^{0} | square metre (centiare) | m^{2} | |

10^{2} | square decametre (are) | dam^{2} | 10^{−2} | square decimetre | dm^{2} | |

10^{4} | square hectometre (hectare) | hm^{2} | 10^{−4} | square centimetre | cm^{2} | |

10^{6} | square kilometre | km^{2} | 10^{−6} | square millimetre | mm^{2} | |

10^{12} | square megametre | Mm^{2} | 10^{−12} | square micrometre | µm^{2} | |

10^{18} | square gigametre | Gm^{2} | 10^{−18} | square nanometre | nm^{2} | |

10^{24} | square terametre | Tm^{2} | 10^{−24} | square picometre | pm^{2} | |

10^{30} | square petametre | Pm^{2} | 10^{−30} | square femtometre | fm^{2} | |

10^{36} | square exametre | Em^{2} | 10^{−36} | square attometre | am^{2} | |

10^{42} | square zettametre | Zm^{2} | 10^{−42} | square zeptometre | zm^{2} | |

10^{48} | square yottametre | Ym^{2} | 10^{−48} | square yoctometre | ym^{2} | |

A square metre is equal to:

- 001 0.000square kilometre (km
^{2}) - 000 square centimetres (cm 10
^{2}) - 0.0001hectares (ha)
- decares (daa) 0.001
- 0.01ares (a)
- deciares (da) 0.1
- 1centiare (ca)
- 247105381 0.000acres
- 710538 0.024cents
- 990 1.195square yards
- 911 10.763square feet
- 550.0031 1square inches

**Square kilometre** or **square kilometer**, symbol **km ^{2}**, is a multiple of the square metre, the SI unit of area or surface area.

The **hectare** is an SI accepted metric system unit of area equal to a square with 100-metre sides, or 10,000 m^{2}, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about 0.405 hectare and one hectare contains about 2.47 acres.

The **acre** is a unit of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one furlong, which is exactly equal to 10 square chains, ^{1}⁄_{640} of a square mile, or 43,560 square feet, and approximately 4,047 m^{2}, or about 40% of a hectare. Based upon the International yard and pound agreement of 1959, an acre may be declared as exactly 4,046.8564224 square metres. The acre is a statute measure in the United States and was formerly one in the United Kingdom and almost all countries of the former British Empire, although informal use continues.

This page is a progressive and labelled list of the SI area orders of magnitude, with certain examples appended to some list objects.

- ↑ David R. Lide, ed. (2010), "INTERNATIONAL SYSTEM OF UNITS",
*CRC Handbook of Chemistry and Physics*(90th ed.)

- BIPM (SI maintenance agency) (home page)
- BIPM brochure (SI reference)

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A **centimetre** or **centimeter** is a unit of length in the metric system, equal to one hundredth of a metre, *centi* being the SI prefix for a factor of 1/100. The centimetre was the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units.

The **kilogram** or **kilogramme** is the base unit of mass in the International System of Units (SI). Until 20 May 2019, it remains defined by a platinum alloy cylinder, the *International Prototype Kilogram*, manufactured in 1889, and carefully stored in Saint-Cloud, a suburb of Paris. After 20 May, it will be defined in terms of fundamental physical constants.

**Kilo** is a decimal unit prefix in the metric system denoting multiplication by one thousand (10^{3}). It is used in the International System of Units where it has the unit symbol **k**, in lower case.

The **litre** or **liter** is an SI accepted metric system unit of volume equal to 1 cubic decimetre (dm^{3}), 1,000 cubic centimetres (cm^{3}) or 1/1,000 cubic metre. A cubic decimetre occupies a volume of 10 cm×10 cm×10 cm and is thus equal to one-thousandth of a cubic metre.

The **metre** or **meter** is the base unit of length in the International System of Units (SI). The SI unit symbol is **m**. The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 second.

**Mega** is a unit prefix in metric systems of units denoting a factor of one million (10^{6} or 1000000). It has the unit symbol **M**. It was confirmed for use in the International System of Units (SI) in 1960. *Mega* comes from Ancient Greek: μέγας, translit. *megas*, lit. 'great'.

The **micrometre** or **micrometer**, also commonly known by the previous name **micron**, is an SI derived unit of length equaling 1×10^{−6} metre ; that is, one millionth of a metre.

The **International System of Units** is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units, which are the ampere, kelvin, second, metre, kilogram, candela, mole, and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies names for 22 derived units, such as lumen and watt, for other common physical quantities.

A **metric prefix** is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in common use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a unique symbol that is prepended to the unit symbol. The prefix *kilo-*, for example, may be added to *gram* to indicate *multiplication* by one thousand: one kilogram is equal to one thousand grams. The prefix *milli-*, likewise, may be added to *metre* to indicate *division* by one thousand; one millimetre is equal to one thousandth of a metre.

The **metric system** is an internationally recognised decimalised system of measurement. It is in widespread use, and where it is adopted, it is the only or most common system of weights and measures. It is now known as the International System of Units (SI). It is used to measure everyday things such as the mass of a sack of flour, the height of a person, the speed of a car, and the volume of fuel in its tank. It is also used in science, industry and trade.

The **pascal** is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal.

* Deca-* or

A **decametre** or **dekameter** is a very rarely used unit of length in the metric system equal to ten metres.

A **unit prefix** is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various sizes are commonly formed by the use of such prefixes. The prefixes of the metric system, such as *kilo* and *milli*, represent multiplication by powers of ten. In information technology it is common to use binary prefixes, which are based on powers of two. Historically, many prefixes have been used or proposed by various sources, but only a narrow set has been recognised by standards organisations.

This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI, because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.

**Sq m** is sometimes used as an abbreviation for Square mile, a unit of surface area in the systems of Imperial and U.S. units and more usually abbreviated to *sq mile* or *sq mi.*

The **cubic metre** or **cubic meter** is the SI derived unit of volume. Its SI symbol is **m ^{3}**. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure. Another alternative name, no longer widely used, was the kilolitre.

The metric system was developed during the French Revolution to replace the various measures previously used in France. The metre is the unit of length in the metric system and was originally based on the dimensions of the earth, as far as it could be measured at the time. The litre, is the unit of volume and was defined as one thousandth of a cubic metre. The metric unit of mass is the kilogram and it was defined as the mass of one litre of water. The metric system was, in the words of French philosopher Marquis de Condorcet, "for all people for all time".