The square metre is the SI derived unit of area, with symbol m2. It is 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 itself 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.
Square kilometre symbol km2, is a multiple of the square metre, the SI unit of area or surface area. 1 km2 is equal to: