One acre is 4,840 square yards or 43,560 square feet, and so a square piece of land measuring 208.71032 feet on all four sides is approximately an acre.The number of sets of dimensions that will equal an acre is infinite.For instance, a piece of land 10 feet wide and 4,356 feet long is exactly one acre because 10 x 4,356 = 43,560. Moreover, a piece of land 30 feet wide and 1,452 feet long is an acre because the two dimensions equal 43,560 square feet when multiplied.or instance, a piece of land 10 feet wide and 4,356 feet long is exactly one acre because 10 x 4,356 = 43,560. Moreover, a piece of land 30 feet wide and 1,452 feet long is an acre because the two dimensions equal 43,560 square feet when multiplied.