Chain (ch)

US & ImperialTraditional unit (still used in some regions)

22 yards or 66 feet (20.1168 m), also called Gunter's chain. A surveying unit; a cricket pitch is one chain long.

1 chain = 20.1168 meters (exactly).

About the chain

Edmund Gunter, an English mathematician, devised a surveying method in 1620 around a measuring chain of 100 links. Its length of 66 feet was chosen because ten square chains make exactly one acre, so land area could be worked out with simple decimal arithmetic. Surveyors' chains had appeared in Dutch and English sources a few years earlier, but his version gave the chain its standard length and its name. John Ogilby's road atlas Britannia, published in 1675, shows it was widely accepted by then.

The chain equals 22 yards, four rods or exactly 20.1168 m, and 80 chains make a mile. Earlier Scots and Irish chains were longer, at about 74 and 84 feet. American public land surveys from the 1785 Land Ordinance relied on it, and sections are 80 chains on a side. The chain also outlived the surveyor's tool itself: a cricket pitch is one chain between the wickets, British railways still give locations in miles and chains, and fire agencies measure spread in chains per hour.

Sources: Wikipedia: Chain (unit); NIST SP 811, Appendix B.8 (length conversion factors)

Chain conversion chart

1 chain expressed in every other length unit:

More US & Imperial units

• inch (length)
• foot (length)
• yard (length)
• mile (length)
• thou (length)
• league (length)
• furlong (length)
• rod (length)
• link (length)
• hand (length)
• pound (weight & mass)
• ounce (weight & mass)
• grain (weight & mass)
• dram (weight & mass)
• cubic inch (volume)
• cubic foot (volume)

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