A hectare is = to 100 'are'
and according to the Britanica it is a metric measure so maybe some consider it not a metric measure but others do and it is based on SI metre and the 'are' but describes 100 'are'

'Hecta' describes 100 units in SI just as 'deca' describes 10 and 'kilo' describes 1,000

https://www.britannica.com/science/hectare
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Hectare, unit of area in the metric system equal to 100 ares, or 10,000 square metres, 

around here a farm is sold as a parcel and the area will be listed but it is not sold 'by the acre'.
If at an auction the bidding is for the whole parcel not by the unit of measure.

Best to describe a hectare by metres and not convert it to other systems then there is not an error in converting.