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History of Systems for Measuring Length

From the beginning of history, humans improvised using what was available to establish measurement systems. The earliest system for measuring length was the human body. Greeks adopted the human body for their measurement units, and the Romans based their method of measure on the Greek system.

While the human body system was convenient and practical for building rough structures, it created confusion for commerce. Because units came from body measurements, the unit sizes varied from region to region and even within a locality. Through much refinement, we now have uniform standards for universally consistent measures.

Today Americans will recognize these units; however, now they have been standardized. While the rest of the world uses the metric system for all purposes, the United States uses two systems; the Metric System and the United States Customary System.

Two wooden rulers showing U.S. systems for measuring length: Customary System and Metric System.

Historical Units of Length

Unit of LengthThenNow
InchWidth of a thumb at the base of the nail1/36th of a yard
Hand5 digits across or 5 inches4 inches
FootLength of the average foot or 11 1/42 inches12 inches
CubitMan’s forearm from the elbow to middle fingertip18 inches
PaceDistance of the human step30 inches
YardLength of man’s girdle or belt36 inches


Different unit sizes between locations caused trade disputes and made commerce between regions difficult. As trade grew between countries, establishing a uniform system for measuring length became more important.

The thumb was an early measurement unit for length. The thumb on the tape measure shows the relationship between an inch and the historical unit for an inch.

To become standardized, everyone has to agree to use the same standard. A standard represents a unit established by an authority. Many years ago, the thumb, hand, and foot were standard measurements for lengths determined by a person of power, such as a king. Objects with etchings made from ivory, wood, or metal bars let everyone know the standards. Authorities placed standards in areas where the public could find them.

Leaders of countries understood that everyone should use the same standard for measuring. Scientists had to find an accurate system to determine the standards. The scientists also needed to find a material and design for the bar that would not shrink, expand, or change shape.

As technology changes, the standard is revised to be more precise. Today, the proton standard bar is a visual representation; however, the standard for length is not a tangible object. Instead, the standard for the length measurement has a description explained as the speed of light.

British Imperial Units of Measure

The British Imperial System derives from the Roman, Saxon, and Norman period’s systems for measuring length.

In 1495, the King of England, King Henry VII, instituted a set of standards known as the Winchester measure. Winchester was the capital city where the standard was. Next, Queen Elizabeth ordered the creation of the Exchequer Standards in 1588. England used the Exchequer Standards until 1824 when the Weights and Measures Act passed.

Beginning in 1824, the British Imperial System was the official system in Great Britain. The British Imperial System, also known as the Imperial Units System, replaced the Winchester and Exchequer Standards. In 1965 the metric system replaced the British Imperial System.

Early Fathers of Metric

John Wilkins

In 1668, John Wilkins (1614-1672), the bishop of Chester located in Cheshire, England, proposed a universal measurement system based on the timing of the swing of a pendulum. He multiplied and divided the standard units by tens, hundreds, and thousands creating the first decimal system.

Gabriel Mouton

Two years later, in 1670, Gabriel Mouton (1618-1694), a French priest, proposed the now-called nautical mile based on one minute of the earth’s arc. He proposed a decimal subdivision system for shorter units. Most consider Gabriel Mouton to be the founding father of the metric system.

Metric Units of Measure

In 1790, the National Assembly of France assigned the French Academy of Sciences to create a consistent standard for all measures. In 1795, France adopted the metric decimal system based on units of 10.

National Prototype No. 27  sent to the United States National Archives represents the metric system of measurement
The modified x-section prototype made from platinum with 10 percent iridium alloy.

The new standard chosen equaled one ten-millionth of the distance between the north pole and the equator. The name given to the new standard of length was mètre (meter), taken from the Greek word metron, meaning a measure.

After the Academy selected the most accurate standard, it was presented to the Council of the Assembly by a delegation of scientists on June 22, 1799. The mètre represented the distance between the polished ends of the bar at a specific temperature. The platinum bar representing the standard is called the “Mètre des Archives.” The Council deposited the mètre (meter) in France’s National Archives.

Copies of the standard were distributed to delegates. The mètre bar for the United States, National Prototype #27, is in the collection at the NIST museum in Gaithersburg, Maryland.

It took another 170 years until Great Britain and Canada adopted the metric system.

Metric Conversions

Millimeter .1 centimeter.01 decimeters.0001 meter
Centimeter10 millimeters .1 decimeter.01 meter 
Decimeter100 millimeters10 centimeters .1 meter
Meter1000 millimeters100 centimeters10 decimeters 

Thomas Jefferson

Thomas Jefferson (1743-1826) recognized the need for a universal measuring system and supported a decimal measurement system. On July 4, 1790, Thomas Jefferson, serving as Secretary of State to President George Washington, presented a report to establish a uniform currency.

Mint Act

In 1792, two years after the National Assembly gathered in France, the United States Congress passed the Mint Act. The decimal currency system established the value of a dollar at 100 cents and had already been established in 13 states when the Mint Act passed.

United States Customary System

The U.S. Customary System derives from the British Imperial System. Three countries: the United States, Liberia, and Myanmar use the Imperial System.

In 1832, the United States adopted the yard as the standard unit of length. The standard for the yard is 3 feet or 36 inches.

Customary length units: inch, foot, yard, and mile.

Inch 0.0833 foot0.0277 yard1.5783e-5 mile
Foot12 inches .333 yard0.000189394 mile
Yard36 inches3 feet 0.000568182 mile
Mile63,360 inches5,289 feet1760 yards 

Treaty of the Mètre

In 1866, an Act passed by Congress legalized the use of the metric system for contracts, dealings, and court proceedings; however, the Act did not mandate its use.

In 1875, the United States was among 16 other countries to sign the Treaty of the Mètre at the Convention of the Mètre held in France. The Treaty of the Mètre (Meter) established the International Bureau of Weights to be directed by the General Conference and situated near Paris.

Bureau of Weights

The Bureau of Weights and Measures is an intergovernmental organization comprised of member governments and associates of the Conférence Générale des Poids et Mesures, CGPM.

General Conference

The General Conference on Weights and Measures is the International Bureau of Weights and Measures’ supreme authority. In 1960, the General Conference revised the metric system, giving the newer system the name International System of Units (S.I.), abbreviated S.I.

Metric Timeline

1781Ratification of the Articles of Confederation
1787The U.S. Constitution is signed, giving Congress the power to fix the standard for measures
1790Ratification of the Constitution
1795France adopts the Metric System
1799The mètre bar is selected and deposited in the National Archives in France
1832Secretary of the Treasury declares the meter as the official U.S. length measure
1866An Act of Congress legalizes the metric system
1875Convention du Métre (Convention of the Meter) established the Treaty of the Métre (Meter)
1893Mendenhall Order is published
1901The National Bureau of Standards (NBS) established
1957The U.S. Army and Marine Corps adopt the metric system
1960S.I., the International System of Units, is established
1965Great Britain adopts the metric system
1970Canada adopts the metric system
1975The Metric Conversion Act is signed
1982The United States Metric Board abolished
1983NIST redefines the meter in terms of the speed of light
1988The Omnibus Trade and Competitiveness Act passes
1991Executive Order 12770 – Metric Usage in Federal Governmental Programs Issued
201860 nations voted unanimously to revise the SI
2019S.I. is revised

Mendenhall Order

April 5, 1893, the Superintendent of Weights and Measures, T.C. Mendenhall, published the “Mendenhall Order,” defining the standard for length as the international meter for both metric and customary measures.

National Institute of Standards (NIST)

Congress established the National Bureau of Standards (NBS) in 1901 and, in 1903, renamed it the Bureau of Standards. Thirty years later, in 1934, the name reverted to the National Bureau of Standards (NBS) again. In 1988 the name changed to the National Institute of Standards and Technology (NIST).

U.S. metric study interim report – A History of the Metric System Controversy in the United States issued in August 1971 was the Tenth in a series of reports prepared by the National Bureau of Standards.

UNT Digital Library offers a free pdf version of A Brief History of Measurement with a Chart of Modernized Metric System. The U.S. National Bureau of Standards published the pamphlet in 1976.

The Modernized Metric System Chart from Brief History of Measurement Systems by the National Bureau of Standards.

United States. National Bureau of Standards. Brief History of Measurement Systems: with a Chart of the Modernized Metric System, pamphlet, August 1976; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc123542/: accessed August 11, 2022), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

In 1986, the National Bureau of Standards updated Weights and Measures Standards of the United States: a brief history by Lewis V. Judson, first published in 1963. The publication details the history of standards of weights and measures sold at $1. Today, NIST provides the publication as a pdf for free.

NIST maintains U.S. standards, which is now part of the U.S. Department of Commerce and is a nonregulatory agency. NIST provides calibrations and standards to the states, and they also enforce the standards. The International Bureau of Weights and Measures, located in France, maintains worldwide uniformity of standards.

The history of systems for measuring length is shown on the Road To The Revised SI shows the history of measure from 1799  to 2019
May 20, 2019
Credit N. Hanacek/NIST

U.S. Metric Board

The Metric Conversion Act sanctioned the metric system as the preferred system of weights and measures for trade and commerce and called for voluntary conversion to the metric system. The Metric Conversion Act of 1975, passed by Congress, established the United States Metric Board (USMB). The board’s function was to provide planning, coordination, and public education in implementing the Metric System.

The U.S. Metric Board dissolved in 1983. The responsibility for voluntary metric conversion moved to the Department of Commerce.

National Institute of Standards and Technology Redefines the Meter

SI, the International System of Units, is the international standard for measurement.

In 1983, the S.I. replaced the meter bar with a new definition. The new description for length is the path traveled by light in a vacuum in 1/299,792,458 of a second. Click here to learn how NIST refined the meter through technology.

Omnibus Trade and Competitiveness Act

In 1988, The Omnibus Trade and Competitiveness Act amended the Metric Conversion act of 1975. The Omnibus Trade and Competitiveness Act’s passing required all Federal agencies to use the metric system.

Executive Order

In response to the slow conversion to metrification, President George Bush issued Executive Order 12770 – Metric Usage in Federal Governmental Programs on July 25, 1991. The order designated the Secretary of Commerce to direct and coordinate metric usage by Federal Departments and agencies. The Secretary of Commerce was authorized to charter an Interagency Council on Metric Policy (ICMP).

The National Institute of Standards and Technology (NIST) chairs The Interagency Council on Metric Policy (ICMP)

Unanimous Vote

A unanimous vote passed on Nov. 16, 2018, at the 26th General Conference of Weights and Measures scientific meeting in Versailles, France. Scientists from 60 countries voted to revise the SI and adopt a system based on the speed of light and constants found in physical science instead of physical objects.

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