When people talk about the chain as a unit they normally mean the unit of the imperial or U.S. system. This is equal to 66 feet or 20.1168 metres. This is also called a Gunter's chain, surveyor's chain or land chain.
In the past people used to use wire chains for measuring land. These chains had 100 links. The links were made of thick wire with a loop at each end. The links were connected to each other by three rings. There were brass handles at each end. People folded the chain up, link by link, and carried it in their hand. The name chain comes from these devices.
Gunter's chain [change]
|1 chain||= 100 links|
|= 66 feet|
|= 4 rods|
|= 1⁄10 furlong|
|= 20.1168 metres|
|10 square chains||= 1 acre|
The chain was also called an acre's breadth. This is because an acre was defined as the area of a rectangle one chain wide and one furlong long.
It is also the length of the pitch, between the wickets, in cricket.
Ramsden's chain [change]
Americans sometimes used a longer chain of 100 feet (30.48 m). This is called the engineer's chain or Ramsden's chain.
Hispanic chain [change]
Texans use another chain for measuring Spanish land grants. This chain is called the Hispanic chain or vara chain. It is based on the vara. A vara is the equivalent of one yard in the old Spanish and Portuguese system of measurement.
|1 vara chain||=20 varas|
|=60 Mexican feet|
|=555⁄9 English feet|
Since in Texas one Mexican foot is defined as 25⁄27 English feet.