Chains to Millimeters (ch to mm)

1 chain equals 20,116.8 millimeters exactly.

1 chain = 20,116.8 millimeters

How to convert chains to millimeters

To convert chains to millimeters, multiply the number of chains by 20,116.8. This factor is exact. To go the other way, multiply millimeters by 0.00004970969538 (rounded).

millimeters = chains × 20,116.8

Example: 10 chains = 201,168 millimeters.

About these units

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.

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.

1 chain = 20.1168 meters (exactly).

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

Millimeter (mm)

Metric (SI)Current unit

One thousandth of a meter. Used in engineering, manufacturing and rainfall measurement.

Carl Friedrich Gauss put the millimeter at the base of his 1832 proposal for absolute units, pairing it with the milligram and the second, although the centimeter-based CGS system later won out among scientists. The name combines the metric prefix milli-, from the Latin for one thousand, with the meter. Since 1983 a millimeter has been tied to the speed of light: it is the distance light covers in 1/299,792,458,000 of a second.

Millimeters are the language of fine mechanical work. Standard rulers are divided into them, digital calipers commonly read to 0.01 mm, and mechanical pencil leads come in 0.5 and 0.7 mm. Copy paper is about 0.1 mm thick, and a thin hair, at 0.02 to 0.04 mm across, is close to the smallest thing the naked eye can see. A wave with a frequency of 300 GHz has a wavelength of 1 mm. An inch is exactly 25.4 mm. One trap for readers in the United States is that mil there traditionally means a thousandth of an inch, not a millimeter.

1 millimeter = 0.001 meters (exactly).

Sources: Wikipedia: Millimetre; Wikipedia: Centimetre-gram-second system of units; NIST Guide to the SI, Appendix B.8: conversion factors

Related conversions

See all length units.