An acre is 43,560 square feet. An acre of land that is in a perfect square shape measures 208 feet, 9 inches on each side.
An acre is a measurement of area and can be any number of dimensions, as long as its area is equal to 43,560 square feet. Because of this, there is not a set length or width for an acre. An acre can be a perfect square or a long skinny area of land.
An acre was originally the amount of land that a farmer could plow in one day with a team of oxen. The farmer normally plowed 1/8 mile up a field and then turned his oxen around and plowed another row. Eighty of these rows in one day was a good day and that area of land became known as an acre.