<Tr> <Td> 1 acre 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 defined as the area of 1 chain by 1 furlong (66 by 660 feet), which is exactly equal to ​ ⁄ of a square mile, 43,560 square feet, approximately 4,047 m, or about 40% of a hectare . </P> <P> The acre is commonly used in many countries, including the United Kingdom, the United States, Canada, India, Ghana, and others . </P>

What is the length and width of a acre