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| tonne | |
|---|---|
| Name | tonne |
| Standard | International System of Units |
| Quantity | mass |
| Units1 | kilograms |
| Units1value | 1000 kg |
tonne The tonne is a metric unit of mass widely used in international trade, science, and engineering. It is defined by an exact mass in the International System of Units and appears in standards, legislation, and industry specifications across many countries and institutions. The term and symbol are used by national laboratories, transport authorities, and standards bodies in coordination with organizations responsible for measurement and trade.
The unit most commonly called tonne corresponds to 1000 kilograms as set by international standards such as those promulgated by International Bureau of Weights and Measures, International Organization for Standardization, International Electrotechnical Commission, European Committee for Standardization, and national metrology institutes like National Institute of Standards and Technology, Physikalisch-Technische Bundesanstalt, and Institut national de recherche et de sécurité. The name arose to distinguish it from imperial and customary units employed in jurisdictions represented by bodies such as National Conference on Weights and Measures and historical institutions like the Board of Trade (United Kingdom). Usage in formal documents often refers to spelling conventions endorsed by lexicographical authorities including Oxford English Dictionary and style guides issued by United Nations agencies, International Monetary Fund, and World Trade Organization.
The modern tonne developed during metrication movements influenced by scientists and statesmen associated with institutions such as the French Academy of Sciences, Conseil des poids et mesures, and later codified during congresses involving delegates from United Kingdom, United States, Germany, France, and other industrializing states. Adoption accelerated through industrial bodies like International Chamber of Commerce, transport regulators such as International Civil Aviation Organization, and regional treaties including those negotiated within the European Union. National legislation enacted by parliaments in countries like Canada, Australia, and Japan integrated the unit into statutory weights and measures regimes administered by agencies such as Standards Australia and Measurement Canada.
Standards defining the tonne are maintained by metrology organizations including International Bureau of Weights and Measures and national labs such as Laboratoire national de métrologie et d'essais and National Research Council (Canada). The SI relationship to the kilogram is exact, and the kilogram itself has been redefined in terms of the Planck constant as realized at facilities like National Physical Laboratory (United Kingdom) and Physikalisch-Technische Bundesanstalt using instruments such as the Kibble balance. Standards documents from International Organization for Standardization and directives from regional authorities like the European Commission specify symbol usage, spelling variants, and legal metrology procedures.
The tonne equals 1000 kilograms and relates to historical units maintained in catalogs by institutions like National Institute of Standards and Technology and libraries such as the British Library. Equivalences with units used in countries represented by organizations like American National Standards Institute include conversion factors to the short ton used in the United States and the long ton historically used in the United Kingdom. Technical manuals from engineering societies including American Society of Mechanical Engineers, Institution of Mechanical Engineers, and transport authorities such as International Maritime Organization provide conversion tables for cargo, shipping, and freight calculations.
Industries from mining corporations listed on stock exchanges like London Stock Exchange and New York Stock Exchange to shipping lines governed by International Maritime Organization conventions use the unit for billing, reporting, and safety standards. Environmental reports submitted to agencies such as the United Nations Framework Convention on Climate Change and standards from International Air Transport Association reference mass inventories in tonne units. Statutory applications appear in legislation drafted by parliaments and ministries in jurisdictions like France, Germany, India, and Brazil, and are enforced by consumer protection agencies and trade regulators including Federal Trade Commission where cross-border trade invokes harmonized measurement rules.
The internationally recommended symbol for the unit is the single-letter symbol t as set out by International Organization for Standardization and endorsed by the International Bureau of Weights and Measures. Style guides produced by institutions such as United Nations Secretariat, European Commission, and national standardizers prescribe use without pluralization and with spacing rules in technical documents. Abbreviations and localized spellings appear in publications from academies such as Royal Society and legal instruments adjudicated in courts like the European Court of Justice when disputes involve contract terms denominated in mass units.
Comparative tables and guidance from bodies like International Organization for Standardization, International Bureau of Weights and Measures, and national metrology institutes contrast the tonne with units such as the short ton, long ton, kilogram, and historical measures cataloged by archives like the National Archives (United Kingdom). Technical standards from engineering societies including American Society for Testing and Materials and trade codes from International Chamber of Shipping clarify contexts where alternative units remain in use and provide protocols for conversion and reconciliation in international contracts and technical specifications.