Chō to Millimeters (chō to mm)

1 chō equals 109,090.9091 millimeters (rounded).

1 chō = 109,090.9091 millimeters

How to convert chō to millimeters

To convert chō to millimeters, multiply the number of chō by 109,090.9091. The factor is rounded to 10 significant digits. To go the other way, multiply millimeters by 0.000009166666667 (rounded).

millimeters = chō × 109,090.9091

Example: 10 chō = 1,090,909.091 millimeters.

About these units

Chō (chō)

JapaneseTraditional unit (still used in some regions)

60 ken, about 109.09 m. A traditional measure of distance along roads and the length of a block.

Cho is written with a character that also means town or block, and the unit appears under the same name for area, which Japanese Wikipedia notes alongside the length meaning. As a length it equals 60 ken, or 360 shaku, putting it between the ken and the ri.

Under the 1891 law it is exactly 1200/11 meter, about 109.09 meters or 358 feet. Because the ken was longer in the 16th century than after the Tokugawa reduction around 1650, a cho measured in an older document may have been several percent longer, so such figures should be treated as approximate.

Thirty-six cho make one ri, so the cho worked as a convenient step for road distances and field layouts. Today it is a historical and place-name unit: the modern metric replacement is simply about 109 meters, roughly one city block.

1 chō = 109.0909091 meters (approximately).

Sources: Wikipedia: Japanese units of measurement; Japanese Wikipedia: Shakkanho (尺貫法); Wikipedia: Ken (unit)

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

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