Unit of Length

A unit of length is a standardized amount of length defined by convention. Length is a fundamental quantity created to measure the distance between two points. There are various unit systems for this physical quantity, the most commonly used are the International System of Units and the Anglo-Saxon system of units.

Length History

Traditionally, ancient societies used the dimensions of the human body as a reference system to measure length. Examples of this were the inch, defined as the width of a thumb, unit foot, defined as the length of a human foot, the yard, which was the distance from the tip of the nose to the tip of the middle finger with the arm extended, the breaststroke, which corresponded to the distance from end to end between the middle fingers with the arms extended, the span, which was the length of the palm of the hand, and the elbow, approximately the length of the forearm. In Ancient Rome units of length were defined for greater distances. Mile was defined as the distance traveled by a Roman legion when taking 2000 steps. A mile equaled eight stadiums and a mile and a half corresponded to approximately one league.

For centuries, each nation defined its own units of length, in most cases, two units named the same way in different countries represented different lengths. This induced the need to define a pattern of universal length, that is, based on physical phenomena accessible anywhere in the world. In 1670, the astronomer and religious Gabriel Mouton proposed as a measurement standard the length of an arc minute of a meridian on Earth. Based on this idea, in 1790, during the French Revolution, the National Assembly decided to define a unit of length as one ten-millionth of the distance of the North Pole to the equator, along the meridian that passes through Dunkerque and Barcelona. This unit came to be known as "metre" or "meter" and would be subdivided into parts of ten, in this way the decimal metric system would emerge. In 1960, the definitions of the units of the metric system were revised and the name of the International System of Units was adopted for the modern version of it.

Conversion table for length

Length Conversion Table of Common Length Units
  Millimeter (mm) Centimeter (cm) Inch (in) Foot/feet (ft) Meter (m)
1 Millimeter (mm) = 1 0.1 0.03937007874015748 0.003280839895013123 0.001
1 Centimeter (cm) = 10 1 0.3937007874015748 0.03280839895013123 0.01
1 Inch (in) = 25.4 2.54 1 0.08333333333333333 0.0254
1 Foot/feet (ft) = 304.8 30.480000000000004 12.000000000000002 1 0.3048
1 Meter (m) = 1000 100 39.37007874015748 3.280839895013123 1