Chain (ch)
The chain is a unit of length equal to 66 feet, 22 yards, or 20.1168 meters. Invented by English mathematician Edmund Gunter in the early 17th century, Gunter's chain was the primary tool for land surveying in the English-speaking world for over 200 years. Its clever design linked imperial distance to imperial area: 10 square chains make one acre.
Definition
One chain equals exactly 66 feet, 22 yards, 4 rods, 100 links, or 20.1168 meters. There are 10 chains in a furlong and 80 chains in a mile. One acre equals exactly 10 square chains (1 chain × 1 furlong). The link, one-hundredth of a chain, equals 7.92 inches or 20.1168 centimeters.
History
Edmund Gunter introduced his surveyor's chain around 1620. It consisted of 100 metal links, each 7.92 inches long, totalling 66 feet. This length was chosen deliberately: one chain times one furlong (10 chains) equals one acre of area, making land area calculations trivially simple. The chain became the standard surveying instrument in England, its colonies, and later the United States. Public land surveys in the US, including the township and range system, were conducted in chains. The chain declined in the 20th century as steel tapes and electronic distance measurement replaced it, but its legacy persists in land records across the English-speaking world.
Common Uses
The chain's legacy lives on in property descriptions, land deeds, and parcel boundaries throughout the US, UK, and former British colonies. Cricket pitches are one chain (22 yards) long. American railroad rights-of-way were often surveyed in chains, and some older US property descriptions still reference chains and links. Modern surveying uses meters or feet, but understanding chains remains essential for interpreting historical land records and legal property descriptions.
Did You Know? Facts About Chain
- A cricket pitch is exactly one chain (22 yards / 20.12 m) long - one of the few surviving everyday uses of the chain.
- Gunter's chain had exactly 100 links, making it an early decimal measuring instrument in an otherwise non-decimal system.
- One acre equals exactly 10 square chains - this was the entire reason Gunter chose 66 feet as the chain length.
- The US Public Land Survey System, which divided western territories into townships and sections, was conducted entirely using chains.
- The phrase "chain of events" has no connection to Gunter's chain - it comes from the metaphor of linked rings.