Convert furlongs to miles

A furlong is a unit of length of 220 yards, that is 660 feet or 201.168 metres[1]. The name comes from the Old English furh, a furrow, and lang, long. The unit measured the length of the furrow a team of oxen could plough without resting[1], so it came straight off the farm.

The mile got its present length only under Queen Elizabeth I, and it was the furlong that fixed it. The Roman mile ran to 5,000 feet, and the queen set the English mile at 5,280 feet, which is exactly eight furlongs[2]. A number that looks arbitrary follows from that one adjustment. Today the statute mile is exactly 1,609.344 metres.

The two units now meet on the racecourse. Race distances across the English-speaking world, Canada and the United States included, are given in miles and furlongs[1], and the Mexican race card prints both forms side by side, for instance “1207.01 METROS (6 F)”[3].

A furlong is 0.125 miles, exactly an eighth of a mile. The mile holds eight of them, and the NIST table gives that figure outright, in a single line: “8 furlongs = 1 mile (mi) = 5 280 feet”[2].

Three numbers come out of that arithmetic, all of them inside the range the commonest races fall into: the English article on horse racing puts that range between five and twelve furlongs[4]. Five furlongs come to 0.625 miles. Eight furlongs make exactly one mile. Twelve furlongs come to one and a half miles.

Every answer ends on an exact figure, because dividing by eight always terminates. That makes the sum easy in your head: take half, then half again, then half once more.

The exactness holds for half-furlong distances too, the kind that appear on American cards. Six and a half furlongs give 0.8125 miles. Eight and a half furlongs give 1.0625 miles. Both land evenly: half a furlong is one sixteenth of a mile.

The formula has one step: miles = furlongs ÷ 8.

Take the distance the Kentucky Derby ran until 1896[5]. Twelve furlongs divided by eight give 1.5 miles. A British race card prints the same distance as 1m 4f and the converter as 1 mi 4 fur, because four furlongs are left once the full mile is taken out.

In metres that comes to 2,414.016 metres. In France the Prix de l’Arc de Triomphe is run over 2,400 metres, so twelve furlongs come out fourteen metres longer.

The other direction is handled by the miles to furlongs converter. If your distance comes in yards or feet, the miles to yards and feet to miles converters take it from there.

British and Irish race cards write a distance longer than a mile with two figures: whole miles first, then the remainder in furlongs. Twelve furlongs are 1 mi 4 fur, and twenty furlongs are 2 mi 4 fur. The converter prints that form under the result field, in the Miles and furlongs line, so you see both at the same time.

The form reads from the left. The first figure says how many whole miles the distance holds, the second how many furlongs are left over. The remainder stops below eight, because eight furlongs make the next whole mile.

The same cards add yards on the end as well. The Grand National runs to four miles and 514 yards in that form[10]. That third part is handled by the miles to yards converter, which takes the 26 mi 385 yd form.

Going the other way, from the two-part form to a number of furlongs, is the job of the miles to furlongs converter. Its input field takes 1 mi 4 fur directly.