<Tr> <Td> 1 ac in...</Td> <Td>... is equal to...</Td> </Tr> <Tr> <Th> SI units </Th> <Td> 4,046.9 m </Td> </Tr> <P> The acre is a unit of land area used in the imperial and US customary systems . It is traditionally defined as the area of one chain by one furlong (66 by 660 feet), which is exactly equal to ​ ⁄ of a square mile, or 43,560 square feet, and approximately 4,047 m, or about 40% of a hectare . </P> <P> The acre is a statute measure in the United States and was formerly one in the United Kingdom and almost all countries of the former British Empire, although informal use continues . </P>

What is the size of an acre of land
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