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Illustration of One Tonne 2018.07.06.png
One tonne is equal to 1000 kilograms or 1 megagram
General information
Unit system Non-SI unit accepted for use with SI
Unit ofMass
In SI base units:1 t = 1000 kg = 1 Mg

The tonne ( /tʌn/ ( Loudspeaker.svg listen ); non-SI unit, symbol: t), commonly referred to as the metric ton Canada, is a non-SI metric unit of mass equal to 1,000  kilograms [1] [2] [3] [4] or one megagram (symbol: Mg). It is equivalent to approximately 2,204.6 pounds, [5] 1.102 short tons (US) or 0.984 long tons (UK). Although not part of the SI, the tonne is accepted for use with SI units and prefixes by the International Committee for Weights and Measures. [6]

This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI, because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.

Mass Quantity of matter

Mass is both a property of a physical body and a measure of its resistance to acceleration when a net force is applied. An object's mass also determines the strength of its gravitational attraction to other bodies.

Kilogram SI unit of mass

The kilogram or kilogramme is the base unit of mass in the International System of Units (SI). Until 20 May 2019, it remains defined by a platinum alloy cylinder, the International Prototype Kilogram, manufactured in 1889, and carefully stored in Saint-Cloud, a suburb of Paris. After 20 May, it will be defined in terms of fundamental physical constants.


The tonne is derived from the mass of one cubic metre of pure water; one thousand litres of pure water has an absolute mass of one tonne.

Cubic metre SI derived unit of volume

The cubic metre or cubic meter is the SI derived unit of volume. Its SI symbol is m3. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure. Another alternative name, no longer widely used, was the kilolitre.

Litre non-SI unit of volume

The litre or liter is an SI accepted metric system unit of volume equal to 1 cubic decimetre (dm3), 1,000 cubic centimetres (cm3) or 1/1,000 cubic metre. A cubic decimetre occupies a volume of 10 cm×10 cm×10 cm and is thus equal to one-thousandth of a cubic metre.

Symbol and abbreviations

The SI symbol for the tonne is 't', adopted at the same time as the unit in 1879. [2] It is a symbol, not an abbreviation, and should not be followed by a period. Use of majuscule and minuscule letter case is significant, and use of other letter combinations is not permitted and would lead to ambiguity. For example, 'T', 'MT', 'Mt', 'mt' are the SI symbols for the tesla, megatesla, megatonne (one teragram) and millitonne (one kilogram) respectively. If describing TNT equivalent units of energy, this is equivalent to 4.184 petajoules.

International System of Units a system of units of measurement for base and derived physical quantities

The International System of Units is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units, which are the ampere, kelvin, second, metre, kilogram, candela, mole, and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies names for 22 derived units, such as lumen and watt, for other common physical quantities.

The tesla is a derived unit of the magnetic induction in the International System of Units.

TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The "ton of TNT" is a unit of energy defined by that convention to be 4.184 gigajoules, which is the approximate energy released in the detonation of a metric ton of TNT. In other words, for each gram of TNT exploded, 4,184 joules of energy are released.

Origin and spelling

In French and most varieties of English (the exceptions being American and occasionally Canadian English), tonne is the correct spelling. It is usually pronounced the same as ton /tʌn/ , but when it is important to clarify that the metric term is meant, rather than short ton, the final "e" can also be pronounced, i.e. "tonny" /ˈtʌnɪ/ . [7] In Australia, it is also pronounced /tɒn/ . [8]

American English Set of dialects of the English language spoken in the United States

American English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. It is considered one of the most influential dialects of English globally, including on other varieties of English.

Canadian English is the set of varieties of the English language native to Canada. According to the 2011 census, English was the first language of approximately 19 million Canadians, or 57% of the population; the remainder of the population were native speakers of Canadian French (22%) or other languages. A larger number, 28 million people, reported using English as their dominant language. 82% of Canadians outside the province of Quebec reported speaking English natively, but within Quebec the figure was just 7.7% as most of its residents are native speakers of Quebec French.

Before metrication in the UK the unit used for most purposes was the Imperial ton of 2,240  pounds avoirdupois or 20 hundredweight (usually referred to as the long ton in the US), equivalent to 1,016 kg, differing by just 1.6% from the tonne. The UK Weights and Measures Act 1985 explicitly excluded from use for trade certain imperial units, including the ton, unless the item being sold or the weighing equipment being used was weighed or certified prior to 1 December 1980, and even then only if the buyer was made aware that the weight of the item was measured in imperial units. [9] [ full citation needed ] [10] [11]

Metrication in the United Kingdom Chronology of metrication and metrication-related events in the United Kingdom

Metrication in the United Kingdom, the process of introducing the metric system of measurement in place of imperial units, has made steady progress since the mid–20th century but today remains equivocal and varies by context. Most of government, industry and commerce use metric units, but imperial units are officially used to specify journey distances, vehicle speeds and the sizes of returnable milk containers, beer and cider glasses. Imperial units are also often used to describe body measurements and vehicle fuel economy. In schools metric units are taught and used as the norm and imperial units that remain in common usage in the UK must also be taught.

Hundredweight unit of mass, with differing values

The hundredweight, formerly also known as the centum weight or quintal, is an English, imperial, and US customary unit of weight or mass of various values. Its value differs between the American and imperial systems. The two values are distinguished in American English as the "short" and "long" hundredweight and in British English as the "cental" and the "imperial hundredweight".

Long ton, also known as the imperial ton or displacement ton, is the name for the unit called the "ton" in the avoirdupois system of weights or Imperial system of measurements. It was standardised in the thirteenth century and is used in the United Kingdom and several other British Commonwealth of Nations countries alongside the mass-based metric tonne defined in 1799.

In the United States metric ton is the name for this unit used and recommended by NIST; [12] an unqualified mention of a ton almost invariably refers to a short ton of 2,000 pounds (907 kg), and tonne is rarely used in speech or writing. Both spellings are acceptable in Canadian usage.

The short ton is a unit of mass equal to 2,000 pounds-mass. The unit is most commonly used in the United States where it is known simply as the ton.

Ton and tonne are both derived from a Germanic word in general use in the North Sea area since the Middle Ages (cf. Old English and Old Frisian tunne, Old High German and Medieval Latin tunna, German and French tonne) to designate a large cask, or tun. [13] A full tun, standing about a metre high, could easily weigh a tonne. An English tun (an old wine cask volume measurement equivalent to nine hundred, and fifty-four litres) of wine has a relative mass of one tonne, nine hundred, and fifty-four kg if full of pure water, a little less for wine.

The spelling tonne pre-dates the introduction of the SI in 1960; it has been used with this meaning in France since 1842, [14] when there were no metric prefixes for multiples of 106 and above, and is now used as the standard spelling for the metric mass measurement in most English-speaking countries. [15] [16] [17] [18] In the United States, the unit was originally referred to using the French words millier or tonneau, [19] but these terms are now obsolete. [3] The Imperial and US customary units comparable to the tonne are both spelled ton in English, though they differ in mass.


One tonne is equivalent to:

Derived units

For multiples of the tonne, it is more usual to speak of thousands or millions of tonnes. Kilotonne, megatonne, and gigatonne are more usually used for the energy of nuclear explosions and other events in equivalent mass of TNT, often loosely as approximate figures. When used in this context, there is little need to distinguish between metric and other tons, and the unit is spelt either as ton or tonne with the relevant prefix attached. [22]

MultipleNameSymbolMultipleNameSymbolTonnes (t)Kilograms (kg)Grams (g)US/short tons (ST)Imperial/long tons (LT)
100tonnet106megagramMg1 t1,000 kg1 million g1.1023 ST0.98421 LT
103kilotonnektǂ109gigagramGg1,000 t1 million kg1 billion g1,102.3 ST984.21 LT
106 megatonne Mt1012teragramTg1 million t1 billion kg1 trillion g1.1023 million ST984,210 LT
109gigatonneGt1015petagramPg1 billion t1 trillion kg1 quadrillion g1.1023 billion ST984.21 million LT
1012teratonneTt1018exagramEg1 trillion t1 quadrillion kg1 quintillion g1.1023 trillion ST984.21 billion LT
1015petatonnePt1021zettagramZg1 quadrillion t1 quintillion kg1 sextillion g1.1023 quadrillion ST984.21 trillion LT
1018exatonneEt1024yottagramYg1 quintillion t1 sextillion kg1 septillion g1.1023 quintillion ST984.21 quadrillion LT

*The equivalent units columns use the short scale large-number naming system currently used in most English-language countries, e.g. 1 billion = 1,000 million = 1,000,000,000.
Values in the equivalent short and long tons columns are rounded to five significant figures, see Conversions for exact values.
ǂThough non-standard, the symbol "kt" is also used for knot, a unit of speed for aircraft and sea-going vessels, and should not be confused with kilotonne.

Alternative usage

A metric ton unit (mtu) can mean 10 kilograms (22 lb) within metal (e.g. tungsten, manganese) trading, particularly within the US. It traditionally referred to a metric ton of ore containing 1% (i.e. 10 kg) of metal. [23] [24] The following excerpt from a mining geology textbook describes its usage in the particular case of tungsten:

"Tungsten concentrates are usually traded in metric tonne units (originally designating one tonne of ore containing 1% of WO3, today used to measure WO3 quantities in 10 kg units. One metric tonne unit (mtu) of tungsten (VI) contains 7.93 kilograms of tungsten." (Walter L Pohl, Economic Geology: Principles and Practices, English edition, 2011, p 183.)

Note that tungsten is also known as wolfram and has the atomic symbol W.

In the case of uranium, the acronym MTU is sometimes considered to be metric ton of uranium, meaning 1,000 kg. [25] [26] [27] [28]

A gigatonne is a unit of mass often used by the coal mining industry to assess and define the extent of a coal reserve.

Use of mass as proxy for energy

The tonne of trinitrotoluene (TNT) is used as a proxy for energy, usually of explosions (TNT is a common high explosive). Prefixes are used: kiloton(ne), megaton(ne), gigaton(ne), especially for expressing nuclear weapon yield, based on a specific combustion energy of TNT of about 4.2  MJ/kg (or one thermochemical calorie per milligram). Hence, 1 t TNT = 4.2  GJ, 1 kt TNT = 4.2  TJ, 1 Mt TNT = 4.2  PJ.

The SI unit of energy is the joule. Assuming that a TNT explosion releases 1,000 small (thermochemical) calories per gram (4.2  kJ/g), one tonne of TNT is equivalent to 4.2 gigajoules.

In the petroleum industry the tonne of oil equivalent (toe) is a unit of energy: the amount of energy released by burning one tonne of crude oil, approximately 42 GJ. There are several slightly different definitions. This is ten times as much as a tonne of TNT because atmospheric oxygen is used.

Unit of force

Like the gram and the kilogram, the tonne gave rise to a (now obsolete) force unit of the same name, the tonne-force, equivalent to about 9.8 kilonewtons: a unit also often called simply "tonne" or "metric ton" without identifying it as a unit of force. In contrast to the tonne as a mass unit, the tonne-force or metric ton-force is not acceptable for use with SI, partly because it is not an exact multiple of the SI unit of force, the newton.

See also

Notes and references

  1. Weights and Measures Act 1985. National Archives (London), 2014. Accessed 13 Aug 2014.
  2. 1 2 Table 6 Archived 2009-10-01 at the Wayback Machine . BIPM. Retrieved on 2011-07-10.
  3. 1 2 "Metric System of Measurement: Interpretation of the International System of Units for the United States" (PDF). Federal Register . 63 (144): 40338. July 28, 1998. 63 FR 40333. Archived from the original (PDF) on October 15, 2011.
  4. The International System of Units (SI) (PDF), 8th Edition, 2006, Section 4.1
  5. United States National Bureau of Standards (1959-06-25). "Notices "Refinement of values for the yard and the pound"" (PDF). Retrieved 2006-08-12.
  6. Corey, Pamela L (1 February 2016). "NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically".
  7. The Oxford English dictionary 2nd ed. lists both /tʌn/ and /ˈtʌnɪ/
  8. Macquarie Dictionary (fifth ed.). Sydney: Macquarie Dictionary Publishers Pty Ltd. 2009.
  9. A Dictionary of Weights, Measures, and Units, edited by Donald Fenna, Oxford University Press
  10. "Weights and Measures Act 1985". Section 8(1), Act No. 72 of 30 October 1985 . Retrieved 11 Apr 2016.
  11. "Weights and Measures Act 1985". Schedule 11(13–14), Act No. 72 of 30 October 1985 . Retrieved 11 Apr 2016.
  12. Metric System of Measurement: Interpretation of the International System of Units for the United States (PDF). See corrections in the Errata section of .
  13. Harper, Douglas. "tonne". Online Etymology Dictionary .
  14. "Recherche d'un mot".
  15. "Guidance Note on the use of Metric Units of Measurement by the Public Sector" (PDF). National Measurement Office. 2007. Archived from the original (PDF) on 2011-02-07. Retrieved 2010-02-13. "Tonne" is listed under "The Principal Metric Units of Measurement" on p. 7.
  16. "National Measurement Regulations 1999 |". Australian Government. 1999. Retrieved 2010-02-13. "Tonne" is listed under Schedule 1, Part 3 as a non-SI unit of measurement used with SI units of measurement.
  17. "Appendix 4: Units of Measurement and Conversion Factors". MAF (Ministry of Agriculture and Forestry (New Zealand)). Retrieved 2010-02-13.
  18. "Canada Gazette". Government of Canada. 1998–2007. Retrieved 2010-02-13. The Corporation shall pay to producers selling and delivering wheat produced in the designated area to the Corporation the following sums certain per tonne basis...
  19. Act of July 28, 1866, codified in 15 U.S.C.   § 205
  20. Barbrow, L.E.; Judson, L.V. (1976). Weights and measures standards of the United States – A brief history. Archived from the original on 2008-05-11.
  21. 1 2 National Institute of Standards and Technology. Butcher, Tina; Crown, Linda; Harshman, Rick; Williams, Juana, eds. (October 2013). "Appendix C – General Tables of Units of Measurement" (PDF). Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. NIST Handbook. 44 (2014 ed.). Washington, D.C.: U.S. Department of Commerce, Technology Administration, National Institute of Standards and Technology. p. C-13. ISSN   0271-4027. OCLC   58927093 . Retrieved 10 December 2013.
  22. The Oxford English Dictionary 2nd ed. gives both megaton and megatonne and adds "The unit may be calculated in either imperial or metric tons; the form megatonne generally implies the metric unit". The use for energy is the first definition; use for mass or weight is the third definition.
  23. "Platt's Metals Guide to Specifications – Conversion Tables". 8 September 2008. Archived from the original on 8 September 2008.CS1 maint: BOT: original-url status unknown (link)
  24. How Many? A Dictionary of Units of Measurement. Retrieved on 2011-07-10.
  25. Reference.Pdf. (PDF) . Retrieved on 2011-07-10.
  26. "Glossary". (June 2000). Disposition of Surplus Hanford Site Uranium, Hanford Site, Richland, Washington. US Department of Energy.
  27. "Acronyms". Y-12 National Security Complex.
  28. NRC Collection of Abbreviations (NUREG-0544, Rev. 4), United States Nuclear Regulatory Commission. (2011-03-13). Retrieved on 2011-07-10.

Related Research Articles

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Orders of magnitude (mass) Orders of magnitude (mass)

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