Chain (length)
As a unit of measurement within the Imperial system, the chain was defined as 22 yards, or 66 feet. Ten chains therefore made one furlong. In metric units, a chain equals 20.1168 metres.
The unit was little used in everyday life even in the heydey of Imperial units in the United Kingdom, and found equally little use within the U.S. customary units. However, it is used to some extent in engineering and surveying in the US.
The chain does however survive, in fact if not always in name, in two specific contexts.
- It is the length of the pitch, between the wickets, in cricket.
- It lies at the origin of the definition of an acre as 4840 square yards. The original acre was an area of land suitable for ploughing in a defined time, and was therefore not square; it measured one chain by one furlong.
In the laying out of towns in Australia and New Zealand, most building plots were originally a "full section" of half an acre, measuring 22 yards by 110. As a consequence, the street frontages of many houses in these countries are one chain long — though as both countries have fully adopted the metric system and a chain is very close to 20 metres, the fact is not always apparent to the houses' inhabitants.
