A square-shaped area measuring 1 acre requires about 835 feet of fencing. An acre encompasses an area of 43,560 square feet, and one side is equal to the square root of this number, which is about 208.7 feet. The perimeter is four times one side, or 4 times 208.7 feet.
If the acre is round, however, the necessary fencing is only 740 feet long. An acre shaped like a trapezoid or a rectangle has a different perimeter as well. Therefore, to determine the amount of fencing that can encompass the perimeter of an acre, it is necessary to know the shape of the area.