Hectare

Arguably, a hectare can be named one of the most commonly used unit of area as it is accepted both by the SI and the Imperial system. A hectare is equal to 10,000 square meters: in other words, it is a piece of area with both length and width of 100 m. It is also 1/100^th of a square km. The symbol accepted for hectare both in SI and the Imperial system is ha.