A furlong is a measure of distance in imperial units and United States customary units equal to one-eighth of a mile, equivalent to any of 660 feet, 220 yards, 40 rods or perches, 10 chains, or approximately 201 metres. It is now mostly confined to use in horse racing, where in many countries it is the standard measurement of race lengths, and agriculture, where it is used to measure rural field lengths and distances specifically in the United Kingdom, Ireland, Canada, and the United States.