Chain (unit)
The chain (abbreviated ch) is a unit of length equal to 66 feet (22 yards), used in both the US customary and Imperial unit systems. It is subdivided into 100 links. There are 10 chains in a furlong, and 80 chains in one statute mile. In metric terms, it is 20.1168 m long. By extension, chainage (running distance) is the distance along a curved or straight survey line from a fixed commencing point, as given by an odometer.
| chain | |
|---|---|
| Unit system | imperial/US units |
| Unit of | length |
| Conversions | |
| 1 chain in ... | ... is equal to ... |
| imperial/US units | 22 yd |
| metric (SI) units | 20.1168 m |
The chain has been used for several centuries in England and in some other countries influenced by English practice. In the United Kingdom, there were 80 chains to the mile, but until the early nineteenth century the Scottish and Irish customary miles were longer than the statute mile; consequently a Scots chain was about 74 (imperial) feet, an Irish chain 84 feet. These longer chains became obsolete following the adoption of the imperial system of units in 1824.
In India, "metric chains" of exactly 20 metres (65.62 feet) are used, along with fractions thereof.