Conversion from Kilometers to Furlongs

Information about the Kilometer (km)

The kilometre is one thousand metres, written km. It is the standard unit for road distance, geographic separation and travel across almost the entire world, and after the metre itself it is the most widely used SI length unit.

Road signs, speed limits, vehicle odometers and navigation systems use it in every country except the United States, Liberia and Myanmar, where miles remain in place. The United Kingdom occupies a middle position: road signs and speed limits are in miles, while most other official measurement is metric. Running and cycling events are almost universally set in kilometres, with the marathon a notable exception at 42.195 km, a distance fixed by the route used at the 1908 London Olympics rather than by any round figure.

The unit suits the human scale of travel. A brisk walk covers about five kilometres in an hour. Urban journeys are typically a few kilometres, and national distances run to hundreds or thousands. Below one kilometre metres are more natural, and above a few thousand many people switch to comparing flight times instead.

Pronunciation is contested. The stress pattern KIL-o-metre follows the pattern of other SI prefixed units such as kilogram and kilowatt, where the prefix is unstressed. The alternative, ki-LOM-eter, is nonetheless dominant in North America and common in Australia and New Zealand, and both are recorded as standard by major dictionaries.

The kilometre also anchors two other units. A square kilometre is one million square metres, or 100 hectares, and is the usual measure for the area of towns, lakes and protected land. Speed is expressed as kilometres per hour, written km/h.

Astronomy uses the kilometre for objects within the solar system, where larger units would be unwieldy. The Moon averages 384,400 km from Earth and the Sun about 149.6 million km. Beyond that distance astronomers switch to astronomical units, light years and parsecs, because the kilometre figures become too long to read. Orbital velocities are given in kilometres per second: the International Space Station travels at roughly 7.66 km/s.

One kilometre equals 1000 metres or 100,000 centimetres. It is approximately 0.621371 miles, so a five-kilometre race is a little over three miles.

Information about the Furlong (fur)

The furlong is a unit of length equal to 220 yards, 660 feet, or exactly 201.168 metres. It is one eighth of a mile and ten chains.

The name is a contraction of the Old English furh lang, meaning furrow long, and describes the distance a team of oxen could plough before needing rest. That practical origin fixed the length of a medieval strip field, and the furlong therefore predates the mile's English definition. When the Roman mile of 5000 feet was reconciled with English land measurement, the mile was lengthened to 5280 feet so that it would contain a whole number of furlongs. The awkward figure that generations of schoolchildren have memorised is a direct consequence of preserving the older agricultural unit.

Horse racing is where the furlong remains in active daily use. Race distances in Britain, Ireland, the United States and much of the racing world are stated in miles and furlongs, so a race described as one mile two furlongs covers 2010 metres. Sectional times are recorded furlong by furlong, and commentary is built around the unit. Distance markers along the rail count down the remaining furlongs to the finish.

The furlong's relationship to area explains its persistence in older records. An acre was originally defined as one furlong long by one chain wide, the area a team could plough in a day. This is why an acre is a long thin rectangle rather than a square, and why its modern value of 43,560 square feet looks arbitrary.

Outside racing the unit is largely archaic, though it appears in some historical land deeds and in the occasional legal description. Computing folklore keeps it alive in the furlong per fortnight, a deliberately absurd unit of speed used to make a point about dimensional analysis.

It is the reason the acre has the shape it does. An acre was defined as one furlong long by one chain wide, 220 yards by 22, and that long thin rectangle is exactly what a team of oxen could plough in a day without turning more often than necessary. The proportion of ten to one is preserved in the ridge and furrow patterns still visible from the air across the English Midlands, and in field boundaries that have outlasted every plough that made them. The furlong therefore survives less as a measurement than as a shape written into the landscape.

One furlong equals 220 yards, 10 chains, one eighth of a mile, or 201.168 metres.