# Square metre

SI unit of area

The square meter is the SI-derived unit of area. It has a symbol m² (33A1 in Unicode). It is defined as the area of a square whose sides measure exactly one metre. The square metre is derived from the SI base unit of the metre, which in turn is defined as the length of the path travelled by light in absolute vacuum during a time interval of 1299,792,458 of a second.

Adding SI prefixes creates multiples and submultiples. However, as the unit is squared, the order of magnitude difference between units doubles from their comparable linear units. For example, a kilometre is one thousand times the length of a metre, but a square kilometre is one million times the area of a square metre.

A "square metre" is not the same thing as a "metre square"  - although it is true that exactly 1 square metre is exactly 1 meter square. But that only works for the numbers 1 and 0; no others.

For example, a square that is 2 metres long and 2 metres wide has 4 square metres of area.

2m * 2m = 4m2

But a square that is 4 metres squared would have 4 metres on each side. This means it would have 16 square metres of area.

4m * 4m = 16m2

That is, (4m)2 is 4 meters squared, whereas 4m2 is 4 square meters.

## SI prefixes applied to the square metre

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

Multiple Name Symbol Multiple Name Symbol 100 square metre (centiare) m² 100 square metre (centiare) m² 102 square decametre (are) dam² 10−2 square decimetre dm² 104 square hectometre (hectare) hm² 10−4 square centimetre cm² 106 square kilometre km² 10−6 square millimetre mm² 1012 square megametre Mm² 10−12 square micrometre µm² 1018 square gigametre Gm² 10−18 square nanometre nm² 1024 square terametre Tm² 10−24 square picometre pm² 1030 square petametre Pm² 10−30 square femtometre fm² 1036 square exametre Em² 10−36 square attometre am² 1042 square zettametre Zm² 10−42 square zeptometre zm² 1048 square yottametre Ym² 10−48 square yoctometre ym²

## Conversions

A square metre is equal to: