Metric system in the United States

From Academic Kids

History and current usage of the metric system in the United States.



In some fields, the metric system has been used in the United States since the early 1800s. The United States has been gradually increasing its use of metric units for many years, but much of the public momentum has been lost since the 1980s, except in schools and science.

19th century

In the early 1800s, the U.S. Coast and Geodetic Survey (the government's surveying and map-making agency) used meter and kilogram standards brought from France. In 1866, Congress authorized the use of the metric system and supplied each state with a set of standard metric weights and measures.

In 1875, the United States solidified their commitment to the development of the internationally recognized metric system by becoming one of the original seventeen signatory nations to the Convention du Mètre. The signing of this international agreement concluded five years of meetings in which the metric system was reformulated, refining the accuracy of its standards. The Treaty of the Meter, also known as the "Meter Convention", established the Bureau international des poids et mesures (BIPM, International Bureau of Weights and Measures) in Sèvres, France, to provide standards of measurement for worldwide use.

In 1893, under the Mendenhall Order, metric standards, developed through international cooperation under the auspices of BIPM, were adopted as the fundamental standards for length and mass in the United States. The customary measurements – the foot, pound, quart, etc. – have been defined in relation to the meter and the kilogram ever since.

20th century

The Conférence Générale des Poids et Mesures (General Conference on Weights and Measures), the governing body that has overall responsibility for the metric system, and which is made up of the signatory nations to the Treaty of the Meter, approved an updated version of the metric system in 1960. This modern system is called Le Système International d'Unités or the International System of Units, abbreviated SI.

The United Kingdom began a transition to the metric system in 1965 to more fully mesh its business and trade practices with those of the European Economic Community. The conversion of the United Kingdom and the Commonwealth nations to SI created a new sense of urgency regarding the use of metric units in the United States.

In 1968, Congress authorized a three-year study of systems of measurement in the U.S., with particular emphasis on the feasibility of adopting SI. The detailed U.S. Metric Study was conducted by the Department of Commerce. A 45-member advisory panel consulted with and took testimony from hundreds of consumers, business organizations, labor groups, manufacturers, and state and local officials.

The final report of the study, "A Metric America: A Decision Whose Time Has Come (," concluded that the U.S. would eventually join the rest of the world in the use of the metric system of measurement. The study found that measurement in the United States was already based on metric units in many areas and that it was becoming more so every day. The majority of study participants believed that conversion to the metric system was in the best interests of the nation, particularly in view of the importance of foreign trade and the increasing influence of technology in American life.

The study recommended that the United States implement a carefully planned transition to predominant use of the metric system over a ten-year period. Congress passed the Metric Conversion Act of 1975 ( "to coordinate and plan the increasing use of the metric system in the United States." The Act, however, did not require a ten-year conversion period. A process of voluntary conversion was initiated, and the U.S. Metric Board was established. The Board was charged with "devising and carrying out a broad program of planning, coordination, and public education, consistent with other national policy and interests, with the aim of implementing the policy set forth in this Act." The efforts of the Metric Board were largely ignored by the American public, and in 1981, the Board reported to Congress that it lacked the clear Congressional mandate necessary to bring about national conversion. Due to this apparent ineffectiveness, and in a Reagan effort to reduce federal spending, the Metric Board was disestablished in the fall of 1982.

The Board's demise increased doubts about the United States' commitment to metrication. Public and private sector metric transition slowed at the same time that the very reasons for the United States to adopt the metric system—the increasing competitiveness of other nations and the demands of global marketplaces—made completing the conversion even more important.

Congress, recognizing the necessity of the United States' conformance with international standards for trade, included new encouragement for U.S. industrial metrication in the Omnibus Trade and Competitiveness Act of 1988. This legislation amended the Metric Conversion Act of 1975 and designates the metric system as "the Preferred system of weights and measures for United States trade and commerce". The legislation states that the Federal Government has a responsibility to assist industry, especially small business, as it voluntarily converts to the metric system of measurement.

Federal agencies were required by this legislation, with certain exceptions, to use the metric system in their procurement, grants and other business-related activities by the end of 1992. While not mandating metric use in the private sector, the Federal Government has sought to serve as a catalyst in the metric conversion of the country's trade, industry, and commerce. Exceptions were allowed for the highway and construction industries (the Department of Transportation eventually reversed position and now requires metric units) while use in the military is very high due to the need to interchange parts with other nation’s militaries.

21st century

Pro-metrication efforts

"Toward a Metric America" (button)

The current effort toward national metrication is based on the conclusion that industrial and commercial productivity, mathematics and science education, and the competitiveness of American products and services in world markets, will be enhanced by completing the change to the metric system of units. Many Americans, however, remain unconvinced of this position.

The most publicized failure caused by confusion of units in the United States was the Mars Climate Orbiter, which was sent to Mars in 1999. This failed due to a programming error, caused by NASA inputting standard SI units into an on-board computer designed for US customary units.

There have been a few anti-metric actions taken by state governments, such as GDOT and FDOT changing exit numbers from actual exit numbers to the nearest milepost number in Georgia and Florida. The blame for this lies in large part with AASHTO standards.

Current usage

Numerous items are produced and sold in metric quantities; however, metric use in general remains low especially for immaterial quantities. Temperature and distance are rarely mentioned in metric quantities and BTUs remain the common measure of heating and cooling. Dual labeling in customary and metric units of goods is required, and in some cases, metric only labeling is allowed. Perhaps the most common metric item sold is the 2-liter of soft drink but attempts to sell 4 liters bottles of milk, instead of gallons, have been largely unsuccessful. Half-liter and one-liter containers of drinks are sold alongside 12 oz., 16 oz. and 20 oz. sizes. Wine is sold in standard bottles of 750 mL and a fifth of liquor, once one fifth of a gallon or 757 mL, are now commonly 750 mL. Photographic film is commonly sold in a 35 mm standard. After a confused period where automobiles were assembled with both customary and metric fasteners in each vehicle, cars are now universally built with metric parts.

In some fields such as science, metric usage is nearly universal. In other fields, such as medicine, usage is mixed. Doctors measure a patient's weight in pounds to compute a dosage of medicine administered in grams or milliliters. The construction industry has been the slowest to adopt metric units, where dimensional lumber still comes in standard 8- and 16-foot lengths and inch widths and depths (although the finished, cured lumber will not actually have the indicated dimensions). Because of Canada's proximity to the U.S., these issues are also still a problem there.

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