Rod (unit)

The rod or perch or pole is a surveyors tool and unit of length equal to 5 yards, 16 feet or of a statute mile and one-fourth of a surveyor's chain. The rod is useful as a unit of length because whole number multiples of it can equal one acre of square measure. The 'perfect acre' is a rectangular area of 43,560 square feet, bounded by sides 660 feet by 66 feet long (660 ft long × 66 ft wide), or 220 yards by 22 yards long (220 yd/ long × 22 yd wide), or 40 rods by 4 rods long. Thus, an acre is 160 square rods. Since the adoption of the international yard on 1 July 1959, the rod has been equal to exactly 5.0292 meters.