Chain (unit)

A chain was a unit of length. It is part of the imperial and United States customary systems. It was used for measuring land. The short way of writing chains is ch.

There are a number of different definitions of the chain, from 50 to 100 feet long. In the imperial system, one chain is equal to 66 feet or 20.1168 metres. This is also called a Gunter's chain, surveyor's chain or land chain.

History and usage

The chain was originally called an "acre's breadth", because it was the width of a acre, while a furlong was the length.

Edmund Gunter, a clergyman and mathematician, invented a measuring device called a chain. The chain was 66 ft (20 m) long. It was divided by 100 in small metal 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.

The unit was once important in everyday life in the United Kingdom and its colonies and in the United States. People used it when they made maps and planned out cities and towns. Land was surveyed and measured using these chains. Even after more accurate ways of measuring land were invented, many people continued to use the chain as a unit because land had already been surveyed in this method for so long.

In England, it is still used in old railways, along with miles. The length of a cricket pitch is one chain.

Gunter's chain

The Gunter's chain is the standard unit.

Standard length
International	Foot	Yard	Chain	Furlong	Mile	Metres
Chain	66	22	1	¹⁄₁₀	¹⁄₈₀	20.1168

Gunter's survey units
International	Link	Rod	Chain	Metres
Chain	100	4	1	20.1168

Other websites

Math Words Archived 2010-06-18 at the Wayback Machine
How Many? A Dictionary of Units of Measurement Archived 2006-12-14 at the Wayback Machine
How to make a Gunter's Chain