Chains to Millimeters
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1 chain (ch) = 20116.8 millimeter (mm). Chain (ch) is a unit of Length used in Standard system. Millimeter (mm) is a unit of Length used in Metric system.

Chain: A Unit of Length Used for Measuring Land

The chain is a unit of length that is equal to 66 feet or 22 yards or 4 rods or 100 links. It is part of the US customary and imperial measurement systems. It is used for measuring land, especially in surveying and mapping. The symbol for chain is ch. There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains. The unit is named after the chain, a measuring device that was invented by Edmund Gunter, a clergyman and mathematician, in the 17th century. The chain is also sometimes called a Gunter’s chain, a surveyor’s chain or a land chain. In this article, we will explore the definition, history, usage and conversion of the chain as a unit of length.

Definition of the Unit

The chain is a unit of length that is equal to 66 feet or 22 yards or 4 rods or 100 links. It is one of the base units in the US customary and imperial measurement systems, along with the foot, the yard and the mile. The chain is also a derived unit in the International System of Units (SI), which is the most widely used system of measurement in the world. The SI base unit of length is the meter, which is defined as the length of the path travelled by light in vacuum during a time interval of 1/299792458 seconds.

The definition of the chain has not changed since its introduction by Edmund Gunter in 1620, who based it on an earlier English unit called an acre’s breadth, which was equal to one-tenth of a furlong or one-eightieth of a mile. However, the definition of the foot, which is used to define the chain, has changed several times over time, as different standards and methods of measurement were adopted by various countries and regions. The current definition of the foot as 0.3048 meter was agreed upon by an international treaty in 1959.

History of the Unit

The origin of the chain as a unit of length can be traced back to 1620, when Edmund Gunter created a measuring device called a chain. The chain was 66 feet long and consisted of 100 metal links connected by three rings each. The links were made of thick wire with a loop at each end. The chain had brass handles at each end for holding and folding. Gunter chose this unit because it was convenient for his work on surveying and mapping land. He also named this unit after himself, as he wrote in his book: "I have taken as unit for these measurements one hundredth part [of a furlong], which I will call an Chain".

Gunter’s unit was soon adopted by other surveyors and mapmakers, who found it useful for measuring distances and areas on flat or gently sloping land. The chain was also used for laying out roads, railways and canals. The chain became part of the US customary and imperial measurement systems, which were based on earlier English units that were brought by British settlers to America. The chain was also used in some other countries influenced by British practice, such as Canada and India.

In 1785, when the United States Congress passed the Land Ordinance Act to survey and divide the public land west of the Appalachian Mountains into rectangular townships and sections, the use of the chain as a unit of measurement was mandated by law. The act also defined the chain as equal to four rods or poles or perches. The surveyors who carried out this work were known as "chain bearers" or "chain carriers", and they marked each mile along their survey lines with wooden posts called "milestones".

In 1959, when the United States, Canada, the United Kingdom and some other Commonwealth countries agreed to adopt a common definition of the foot as 0.3048 meter, based on the international yard that was defined as 0.9144 meter by an international treaty in 1959, the chain became exactly equal to 20.1168 meters.

Usage of the Unit

The chain is a unit of length that is used for measuring land, especially in surveying and mapping. The chain is also used for measuring distances on roads, railways and canals. The chain is still used in some rural areas and historical contexts in the United States, Canada and some other countries that follow the US customary or imperial measurement systems.

The chain is used for various purposes, such as:

• Measuring length, width and area of land parcels and properties.
• Measuring distances and dimensions on maps and plans.
• Measuring boundaries and borders between states, counties and townships.
• Measuring road widths and lengths.
• Measuring railway track gauges and lengths.
• Measuring canal widths and depths.

How to Convert

The chain can be converted to other units of length by using conversion factors or formulas. Here are some examples of how to convert chains to other units of length in the US customary system, the imperial system and the SI system:

• To convert chains to feet, multiply by 66. For example, 10 ch = 10 × 66 = 660 ft.
• To convert chains to yards, multiply by 22. For example, 10 ch = 10 × 22 = 220 yd.
• To convert chains to miles, divide by 80. For example, 10 ch = 10 / 80 = 0.125 mi.
• To convert chains to centimeters, multiply by 2011.68. For example, one ch = one × 2011.68 = 2011.68 cm.
• To convert chains to meters, multiply by 20.1168. For example, one ch = one × 20.1168 = 20.1168 m.
• To convert chains to kilometers, divide by 49.7097. For example, 10 ch = 10 / 49.7097 = 0.2012 km.

Equivalents in Other Units and Scales

The chain can be expressed in terms of other units of length by using equivalent values or ratios. Here are some examples of how to express chains in other units of length:

• One chain is equal to four rods or poles or perches.
• One chain is equal to one-tenth of a furlong or one-eightieth of a mile.
• One chain is equal to one-hundredth of a league or one-fortieth of a league (US).
• One chain is equal to one-hundred-millionth of an astronomical unit or one-forty-billionth of a light-year.
• One chain is equal to one-thousandth of a nautical mile or one-three-thousand-six-hundredth of a degree of latitude or longitude.

Millimeter: A Unit of Length

Definition of the millimeter

A millimeter is a unit of length in the metric system, which is based on the International System of Units (SI). It is defined as one thousandth of a meter, which is the SI base unit of length. One millimeter can be written as 1 mm or 0.001 m.

How to convert millimeter to other units of length

To convert millimeter to other units of length, we need to use conversion factors that relate the millimeter to the desired unit. For example, to convert millimeter to centimeter, we need to know that 1 cm = 10 mm, so we can divide the number of millimeters by 10 to get the number of centimeters. Similarly, to convert millimeter to inch, we need to know that 1 in = 25.4 mm, so we can divide the number of millimeters by 25.4 to get the number of inches.

Here are some common conversion factors for millimeter and other units of length in the US standard system and the SI system:

• 1 mm = 0.1 cm
• 1 mm = 0.03937 in
• 1 mm = 0.001 m
• 1 mm = 0.000001 km
• 1 mm = 0.00000062137 mi
• 1 mm = 0.00000053996 nmi

Where millimeter is used

The millimeter is a widely used unit of length in many fields and applications around the world. Some examples are:

• In engineering and manufacturing, the millimeter is often used to measure small dimensions and tolerances of parts and products.
• In medicine and biology, the millimeter is often used to measure the size and growth of cells, tissues, organs, and microorganisms.
• In astronomy and physics, the millimeter is often used to measure the wavelength and frequency of electromagnetic radiation, such as radio waves and microwaves.
• In geography and cartography, the millimeter is often used to measure the scale and distance on maps and globes.
• In art and design, the millimeter is often used to measure the thickness and width of lines, shapes, and fonts.

History of millimeter

The millimeter has a long and varied history in different countries and cultures. Some historical facts are:

• The first recorded use of the millimeter as a unit of length was in France in the late 18th century, during the French Revolution. The French Academy of Sciences adopted the metric system as a standard for measurement and defined the meter as one ten-millionth of the distance from the equator to the pole.
• The millimeter was officially recognized as a part of the SI system in 1960, when the General Conference on Weights and Measures (CGPM) adopted a new definition of the meter based on the wavelength of light emitted by a krypton-86 atom.
• The millimeter is still widely used today in many countries that have adopted the metric system, such as most of Europe, Asia, Africa, and Latin America. However, some countries still use other units of length alongside or instead of the millimeter, such as the United States, Canada, and the United Kingdom.

Example conversions of millimeter to other units

Here are some examples of how to convert millimeter to other units of length using the conversion factors given above:

• To convert 5 mm to cm, we divide by 10: 5 mm / 10 = 0.5 cm
• To convert 12 mm to in, we divide by 25.4: 12 mm / 25.4 = 0.47244 in
• To convert 100 mm to m, we divide by 1000: 100 mm / 1000 = 0.1 m
• To convert 250 mm to km, we divide by 1000000: 250 mm / 1000000 = 0.00025 km
• To convert 500 mm to mi, we divide by 1609344: 500 mm / 1609344 = 0.00031069 mi
• To convert 1000 mm to nmi, we divide by 1852000: 1000 mm / 1852000 = 0.00053996 nmi