Furlong
| Furlong | |
|---|---|
| Unit system | imperial/US units |
| Unit of | length |
| 1 furlong in ... | ... is equal to ... |
| imperial/US units | 220 yd |
| metric (SI) units | 201.1680 m |
A furlong is a measure of distance in imperial units and U.S. customary units equal to one-eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, or 10 chains. Using the international definition of the inch as exactly 25.4 millimetres, one furlong is 201.168 metres. However, the United States does not uniformly use this conversion ratio. Older ratios are in use for surveying purposes in some states, leading to variations in the length of the furlong of about two parts per million, or 0.4 millimetres ( 1⁄64 inch). This variation is too small to have many practical consequences. Five furlongs are about 1.0 kilometre (1.00584 km is the exact value, according to the international conversion).
The name furlong derives from the Old English words furh (furrow) and lang (long). Dating back at least to early Anglo-Saxon times, it originally referred to the length of the furrow in one acre of a ploughed open field (a medieval communal field which was divided into strips). The system of long furrows arose because turning a team of oxen pulling a heavy plough was difficult. This offset the drainage advantages of short furrows and meant furrows were made as long as possible. An acre is an area that is one furlong long and one chain (66 feet or 22 yards) wide. For this reason, the furlong was once also called an acre's length, though in modern usage an area of one acre can be of any shape. The term furlong, or shot, was also used to describe a grouping of adjacent strips within an open field.
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