A furlong's a measure of distance in imperial units and U.S. customary units. It's equal to one-eighth of a mile, 220 yards, 660 feet, 201.168 meters, or 10 chains. Five furlongs are approximately 1 kilometer (1.00584 km to be exact). Since the original definition of the meter was one-quarter of one ten-millionth of the circumference of the Earth (along the great circle coincident with the meridian of longitude passing through Paris), the circumference of the Earth's about 40,000 km or about 20… (More on Furlongs)