Quick answer: A tonne (metric ton) is exactly 1,000 kg. A long ton, the old British ton, is 2,240 lb, or 1,016.05 kg. A short ton, the everyday American ton, is 2,000 lb, or 907.18 kg. So the long ton is about 1.6% heavier than a tonne, and the short ton is about 9.3% lighter.
Three different units share almost the same name, and mixing them up can put a quote, a shipping weight or a school answer out by nearly a tenth. This explainer sets out how each one is defined, where you will still meet it, and how to convert between them. For the wider picture of kilograms, pounds and stones, see the weight conversions hub.
What is the difference between a tonne, a long ton and a short ton?
They are three separate units: the tonne is metric (1,000 kg), the long ton is British imperial (2,240 lb) and the short ton is American (2,000 lb). All three grew out of the idea of a large, round “load”, but each system rounded it differently.
The tonne is built on the kilogram, so it is simply 1,000 kg, or one megagram. The long ton is 20 imperial hundredweight of 112 lb each. The short ton is 20 American hundredweight of 100 lb each. Because both imperial tons are defined in pounds, and the pound is defined as exactly 0.45359237 kg, their metric values are exact too.
| Unit | Definition | Kilograms | Pounds | Main users |
|---|---|---|---|---|
| Tonne (t) | 1,000 kg | 1,000 kg | 2,204.62 lb | UK, Europe and most of the world |
| Long ton | 20 cwt × 112 lb | 1,016.05 kg | 2,240 lb | Historic UK, some shipping |
| Short ton | 20 cwt × 100 lb | 907.18 kg | 2,000 lb | United States |
Which ton does the UK use today?
The UK uses the metric tonne for trade, road signs, freight and official statistics. The long ton still exists in law, but only as a supplementary unit.
Schedule 1 of the Weights and Measures Act 1985 defines the tonne (or metric tonne) as 1,000 kilograms and the ton as 2,240 pounds. The ton, hundredweight, quarter and stone sit in the part of the schedule for units that may not be used for trade except as supplementary indications. In practice, that means a builders’ merchant sells aggregate by the tonne, a weight-limit sign on a bridge shows a figure such as “7.5 t”, and any mention of tons alongside is extra information.
The old units survive in conversation. Older relatives may still talk about coal by the hundredweight, and “a ton” is common slang for a hundred of something, from a century in cricket to 180 in darts being “a ton-eighty”. Those uses are figures of speech rather than weights.
Is a metric ton the same as a tonne?
Yes. “Metric ton” is the American name for the tonne, and both mean exactly 1,000 kg. The US National Institute of Standards and Technology lists 1,000 kilograms as one megagram (Mg), or one metric ton (t).
Watch out for the abbreviation “MT” in American documents. It is often used for metric tons, but it can be confused with “megatonne” (Mt, a million tonnes) or simply misread. The SI symbol for the tonne is a lower-case t, so 25 t means 25 tonnes. If a document only says “tons” and comes from the US, assume short tons unless it states otherwise.
How do you convert tonnes to long tons and short tons?
Multiply tonnes by 0.9842 to get long tons, or by 1.1023 to get short tons. Going the other way, multiply long tons by 1.01605 or short tons by 0.90718 to get tonnes.
- Long tons = tonnes × 0.984207
- Short tons = tonnes × 1.102311
- Short tons = long tons × 1.12 (exactly, because 2,240 ÷ 2,000 = 1.12)
- Long tons = short tons × 0.892857
Worked example: a 7.5-tonne weight limit is 7.5 × 0.984207 = 7.38 long tons, or 7.5 × 1.102311 = 8.27 short tons. A US report of 50 short tons of steel is 50 × 0.907185 = 45.36 tonnes.
| Tonnes | Long tons | Short tons | Pounds |
|---|---|---|---|
| 1 t | 0.984 | 1.102 | 2,205 lb |
| 2 t | 1.968 | 2.205 | 4,409 lb |
| 3.5 t | 3.445 | 3.858 | 7,716 lb |
| 7.5 t | 7.382 | 8.267 | 16,535 lb |
| 10 t | 9.842 | 11.023 | 22,046 lb |
| 20 t | 19.684 | 22.046 | 44,092 lb |
| 50 t | 49.210 | 55.116 | 110,231 lb |
| 100 t | 98.421 | 110.231 | 220,462 lb |
For the reverse direction, this table starts from the imperial and US units.
| Amount | Long tons in tonnes | Short tons in tonnes |
|---|---|---|
| 1 | 1.016 t | 0.907 t |
| 2 | 2.032 t | 1.814 t |
| 5 | 5.080 t | 4.536 t |
| 10 | 10.160 t | 9.072 t |
| 20 | 20.321 t | 18.144 t |
| 100 | 101.605 t | 90.718 t |
For anything smaller than a tonne, the kg to lb converter handles the pounds side directly.
Why are there two different hundredweights?
The British hundredweight is 112 lb and the American hundredweight is 100 lb, and that single difference explains the gap between the long and short ton. Both systems agree that 20 hundredweight make a ton.
In the British system the chain runs 14 lb to the stone, 2 stone (28 lb) to the quarter, 4 quarters (112 lb) to the hundredweight, and 20 hundredweight to the ton. The US dropped the stone and the quarter and rounded the hundredweight to an even 100 lb, which is why its ton is an even 2,000 lb. One British hundredweight is 50.80 kg; one US hundredweight is 45.36 kg.
| Step | British (long) system | US (short) system |
|---|---|---|
| Hundredweight (cwt) | 112 lb = 50.80 kg | 100 lb = 45.36 kg |
| Hundredweights per ton | 20 | 20 |
| Ton | 2,240 lb = 1,016.05 kg | 2,000 lb = 907.18 kg |
Where will you still see long tons and short tons?
Long tons turn up mainly in historical and naval records; short tons are everyday units in the United States. If you read older British sources, assume “tons” means long tons.
- Warship displacement. Many historical and some current naval figures give displacement in long tons.
- Old British statistics. Coal, steel and harvest records from before metrication are in imperial tons and hundredweight.
- US vehicles and materials. American truck ratings, gravel, coal and scrap prices usually use short tons.
- International trade and science. Commodity markets, emissions reporting and research papers almost always use tonnes.
Are there “tons” that are not weights at all?
Yes. Ship gross tonnage, refrigeration tons and tons of TNT are not masses, so none of the conversions above apply to them. They borrowed the word but measure something else.
- Gross tonnage of a ship is calculated from its enclosed volume, not its weight.
- A ton of refrigeration, used for American air-conditioning, is a cooling rate of 12,000 BTU per hour, about 3.5 kW.
- A ton (or tonne) of TNT is a conventional unit of energy for explosions, set at 4.184 gigajoules.
When does the difference really matter?
It matters whenever you are paying, loading or comparing by the ton, because a short ton is almost 93 kg lighter than a tonne. On a 20-tonne load, reading the figure as short tons instead understates the mass by 1.86 tonnes.
Common mistakes to avoid:
- Assuming an American “ton” is a tonne. It is a short ton unless the source says “metric”.
- Converting an old British “ton” as 2,000 lb. Pre-metric UK tons are 2,240 lb.
- Writing “T” or “Mt” when you mean tonnes. The tonne symbol is a lower-case t.
- Treating gross tonnage or air-conditioning “tons” as a weight.
To see how the tonne fits into the metric ladder of grams and kilograms, the guide to units of measurement sets out every step, and the UK measurement system hub explains why imperial units hang on in everyday life.
Frequently asked questions
Which is heavier, a ton or a tonne?
It depends which ton. A UK long ton (1,016.05 kg) is slightly heavier than a tonne (1,000 kg), while a US short ton (907.18 kg) is lighter.
How many pounds are in a tonne?
A tonne is 2,204.62 lb. A long ton is exactly 2,240 lb and a short ton is exactly 2,000 lb.
How many short tons are in a long ton?
Exactly 1.12 short tons, because 2,240 lb divided by 2,000 lb is 1.12. One short ton is about 0.893 long tons.
Is the imperial ton still legal in the UK?
The ton of 2,240 lb is still defined in the Weights and Measures Act 1985, but for trade it may only be used as a supplementary indication alongside the metric tonne.
What is the symbol for a tonne?
The symbol is a lower-case t, as in 3.5 t. The long and short tons have no SI symbol, so write the unit name in full.
Sources
- Weights and Measures Act 1985, Schedule 1 (legislation.gov.uk)
- SI units: mass (NIST Office of Weights and Measures)
- The International System of Units (BIPM)