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Chains explained

The chain is a traditional unit of length used mainly in surveying and land measurement. Originally standardized as the Gunter's chain, the chain remains significant in historical land records, surveying practice, and some legal descriptions of property.

Symbol

The common symbol for the chain is ch. Older texts may simply spell out "chain" or use surveyor shorthand.

Chain in Imperial and US customary units

Unit Symbol Description
Mile mi 1 mile = 80 chains
Furlong fur 1 furlong = 10 chains
Chain (base unit) ch Gunter's chain = 66 feet = 22 yards = 4 rods
Rod (also pole or perch) rd 1 rod = 16.5 feet = 0.25 chain
Link li 1 link = 0.66 feet; 1 chain = 100 links

Comparison with other unit systems

The chain belongs to the imperial/US customary family of units and is not part of the SI system. For metric comparison, 1 chain = 20.1168 meters. Modern surveying generally uses meters, but chains appear in legacy records and some regional practices.

Uses and practical applications

The chain is historically important in cadastral surveying, property deeds, land subdivision, and mapping. Today it is most often encountered in historical land documents, legal descriptions, and teaching about surveying history.

  • Interpreting historical property deeds and boundary descriptions
  • Cadastral surveying and land registry research
  • Teaching surveying methods and history
  • Converting legacy measurements to modern units

Instruments and measurement

The original tool is the Gunter's chain (surveyor's chain), a physical chain of 100 links totaling 66 feet. Modern alternatives include steel survey tapes, total stations, and GNSS/GPS survey equipment that replace physical chains while preserving unit conversions.

Sketch of a Gunter's chain (surveyor's chain)

Origin

The standardized surveying chain is attributed to Edmund Gunter, a 17th-century English mathematician and surveyor who introduced the Gunter's chain to simplify land measurement and calculation.

FAQs about the chain

Why is a surveying chain 66 feet long?

Gunter chose 66 feet because it divides evenly into common land-measurement units: 10 chains make a furlong and 80 chains make a statute mile. The length also yielded convenient relationships with acres (see next question).

How does the chain relate to acres?

One acre equals 10 square chains (an area one chain wide by ten chains long). This made area calculations straightforward when using the Gunter's chain in the field.

Is the chain still used for legal descriptions today?

Yes. Many older deeds and cadastral records use chains; surveyors convert those values to modern units when preparing new plans. Some jurisdictions still accept legacy descriptions that reference chains.

How long is a physical Gunter's chain and how is it constructed?

A Gunter's chain typically has 100 links and measures 66 feet in total. Links and rings are durable metal, and the chain often folds for transport. Specialized survey tapes and electronic equipment now replace it in practice.

Can I convert chains to meters or feet easily?

Yes. 1 chain = 66 feet = 20.1168 meters. Use that factor for precise conversions when translating historical measurements into metric units for mapping

How do I convert chains to other length units?

Use the links below for easy conversions from chains to other length units available on this website.