Acres vs Hectares

• 11 hectare = 2.47105 acres, so a hectare is roughly two and a half acres. Conversely 1 acre = 0.404686 ha.
• 2The acre is not square. It is defined as one chain by one furlong — 66 ft by 660 ft — a shape that comes from ploughing practice rather than geometry. The hectare is square by construction.
• 3Both are legacy units in the sense that neither is SI. The SI area unit is the square metre; the hectare is accepted for use with SI specifically because land area in square metres produces unwieldy numbers.
• 4Land registries differ by country and sometimes by state, so property documents may use either. UK land registry data uses hectares; US deeds use acres.
• 5Forestry, agricultural subsidy schemes and carbon accounting are almost universally hectare-based, including in countries whose farmers still speak in acres.

The acre is one of the oldest units still in daily use, and its odd size is a fossil of medieval agriculture: a furlong was the distance a team could plough before resting, and a chain was a convenient surveying length. The hectare arrived with the metric system as a deliberately round alternative — 100 m by 100 m — but adoption was slow in English-speaking farming communities precisely because the acre was tied to how land had been worked and traded for a thousand years.