hectare

Non-SI unit accepted for use with SI

Name	Symbol	Quantity	SI units
hectare	ha	area	10⁴ m²
The hectare, symbol ha, is a non-SI unit of area accepted for use with the SI. One hectare is equal to one square hectometre, symbol hm², or 10 000 m².
Definition			c² Δν_Cs^-2
$1 \mspace{4mu} \text{ha} \mspace{6mu} = \dfrac{(10^4) (9 \mspace{4mu} 192 \mspace{4mu} 631 \mspace{4mu} 770)^2}{(299 \mspace{4mu} 792 \mspace{4mu} 458)^2} \mspace{6mu} \dfrac{c^2}{{\Delta \nu _{Cs}}^2}\\ \\ \\ 1 \mspace{4mu} \text{ha} \mspace{6mu} \approx 9.402 \mspace{4mu} 391 \mspace{4mu} 313 \mspace{4mu} 904 \mspace{4mu} 046 \mspace{4mu} 861 \times10^{6} \mspace{6mu} c^2 \mspace{4mu} {\Delta \nu _{Cs}}^{-2}$

Originally one hectare meant 100 ares, where one are was a unit equal to 100 m². The are is now obsolete, but the hectare remains as a unit accepted for use with the SI.

The hectare is used mostly as a unit to express land areas. There are 100 hectares in one square kilometre.

The non-SI unit hectare, symbol ha, is equal in size to the SI unit square hectometre, symbol hm².

1 ha	= 10 000 m²	= 1 hm²
100 ha	= 100 hm²	= 1 km²

Note: SI prefixes must not be used with the hectare.