The square metre (also spelled square meter, see spelling differences) is the SI derived unit of area, with symbol m^{2} (33A1 in Unicode^{[1]}). 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 ^{1}⁄_{299,792,458} of a second.
Adding and multiplying 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.
Square metres are not necessarily the same as meters squared^{[2]}: an area 2 metres wide by 5 metres long would be 10 square metres, while 10 metres squared means an area of 10 metres by 10 metres. So 10 metres squared equals 100 square meters.
Contents 
The square metre may be used with all SI prefixes used with the metre.
Multiplication  Name  Symbol  plusing  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:
Orders of magnitude for area  

1 E30 m² = 1 fm^{2}  1 E24 m² = 1 pm^{2}  1 E18 m² = 1 nm^{2}  1 E12 m² = 1 µm^{2}  1 E6 m² = 1 mm^{2}  1 E0 m² = 1 m^{2}  1 E+6 m² = 1 km^{2}  1 E+12 m² = 1 Mm^{2}  1 E+1824 m² : 1 Gm^{2} 
10 fm^{2}  10 pm^{2}  10 nm^{2}  10 µm^{2}  10 mm^{2}  10 m^{2}  10 km^{2}  10 Mm^{2}  > 1 E+24 m² : 1 Tm² 
100 fm^{2}  100 pm^{2}  100 nm^{2}  100 µm^{2}  100 mm^{2} = 1 cm^{2}  100 m^{2} = 1 a  100 km^{2}  100 Mm^{2}  
1,000 fm^{2}  1,000 pm^{2}  1,000 nm^{2}  1,000 µm^{2}  10 cm^{2}  10 a  1,000 km^{2}  1,000 Mm^{2}  
10,000 fm^{2}  10,000 pm^{2}  10,000 nm^{2}  10,000 µm^{2}  100 cm^{2}  10,000 m^{2} = 1 ha  10,000 km^{2}  10,000 Mm^{2}  
100,000 fm^{2}  100,000 pm^{2}  100,000 nm^{2}  100,000 µm^{2}  1,000 cm^{2}  10 ha  100,000 km^{2}  100,000 Mm^{2}  
SI derived unit square metre, from base unit metre  Conversion of units for area 
