A tonne (also called a metric ton) is exactly 1,000 kg, or about 2,204.6 lb. A US short ton is 2,000 lb, which is 907.18 kg. A British long ton is 2,240 lb, which is 1,016.05 kg. So the three “tons” differ by up to 12%: the long ton is the heaviest, the tonne sits in the middle, and the US short ton is the lightest.
How do the three tons compare? #
| Unit | Also called | Pounds | Kilograms | Used mainly in |
|---|---|---|---|---|
| Short ton | US ton, “ton” in the US | 2,000 | 907.18474 | United States |
| Tonne | Metric ton | 2,204.62 | 1,000 | Most of the world, science, trade |
| Long ton | Imperial ton, UK ton | 2,240 | 1,016.0469088 | Older UK records, some shipping |
All three kilogram figures are exact, because the pound is defined as exactly 0.45359237 kg. NIST SP 811 lists the short ton at 907.1847 kg.
In percentages: a tonne is about 10.2% heavier than a short ton, and a long ton is about 1.6% heavier than a tonne.
Why are there three tons? #
They all come from the same idea: a ton was a big, round load of goods. In the British system, the hundredweight was 112 lb (8 stone), and 20 hundredweight made a long ton of 2,240 lb. The US kept the ton but settled on a 100 lb hundredweight, so its 20-hundredweight ton is 2,000 lb. The metric system then defined its own tonne as 1,000 kg, roughly the mass of a cubic meter of water.
The spelling helps in writing: “tonne” almost always means 1,000 kg. In speech, “ton” and “tonne” sound the same, which is where the confusion starts. In US government and trade documents, “metric ton” is the usual name for the tonne.
Tonnes to short tons and long tons #
| Tonnes | Short tons (US) | Long tons (UK) | Pounds |
|---|---|---|---|
| 1 | 1.102 | 0.984 | 2,205 |
| 2 | 2.205 | 1.968 | 4,409 |
| 5 | 5.512 | 4.921 | 11,023 |
| 10 | 11.023 | 9.842 | 22,046 |
| 20 | 22.046 | 19.684 | 44,092 |
| 25 | 27.558 | 24.605 | 55,116 |
| 50 | 55.116 | 49.210 | 110,231 |
| 100 | 110.231 | 98.421 | 220,462 |
| 1,000 | 1,102.311 | 984.207 | 2,204,623 |
Short tons to tonnes #
| Short tons | Tonnes | Long tons |
|---|---|---|
| 1/2 | 0.454 | 0.446 |
| 1 | 0.907 | 0.893 |
| 2 | 1.814 | 1.786 |
| 5 | 4.536 | 4.464 |
| 10 | 9.072 | 8.929 |
| 20 | 18.144 | 17.857 |
| 40 | 36.287 | 35.714 |
| 100 | 90.718 | 89.286 |
The mental shortcut #
1 tonne ≈ 1.1 short tons, and 1 short ton ≈ 0.9 tonnes. Both are within about 1%. A long ton is close enough to a tonne (1.6% apart) that for rough figures you can treat them as equal, but not on a bill of lading.
Worked examples #
A car weighs 1.5 tonnes. 1.5 × 1.1023 = 1.65 short tons, or 3,307 lb.
A shipping container holds 20 tonnes of cargo. That’s 22.05 short tons. If a US buyer quotes a price “per ton,” check whether they mean short tons, or you’ll be off by about 10%.
A US gravel supplier sells by the ton. A US ton is 2,000 lb, so 5 tons of gravel is 10,000 lb, or 4.54 tonnes.
An old British shipping record lists 500 tons. If it predates metrication, it’s probably long tons: 500 × 1.016 = 508 tonnes.
Other “tons” that aren’t weights at all #
Several industries use “ton” for something else entirely. If a number doesn’t make sense as a weight, it may be one of these:
| Unit | What it measures | Value |
|---|---|---|
| Ton of refrigeration | Cooling power (air conditioners) | 12,000 BTU per hour, about 3.52 kW |
| Register ton | Ship’s internal volume | 100 cubic feet, about 2.83 m³ |
| Ton of TNT | Energy (explosions) | By convention, 4.184 gigajoules |
The air-conditioning ton is the one most people meet. It dates back to the cooling power of melting a ton of ice over a day, and it’s defined as 12,000 BTU per hour. A “3-ton” home air conditioner moves 36,000 BTU/h of heat, which is 10.55 kW.
| AC size | BTU per hour | Kilowatts |
|---|---|---|
| 1 ton | 12,000 | 3.52 |
| 1.5 tons | 18,000 | 5.28 |
| 2 tons | 24,000 | 7.03 |
| 2.5 tons | 30,000 | 8.79 |
| 3 tons | 36,000 | 10.55 |
| 4 tons | 48,000 | 14.07 |
| 5 tons | 60,000 | 17.58 |
“Half-ton” and “three-quarter-ton” pickup trucks are another trap. Those names are old class labels. Today they don’t tell you the truck’s payload, which is listed on the door-jamb sticker and in the owner’s manual.
Converting tons on your phone #
Convert Units Calculator has metric tons and US short tons in its Weight category, alongside kilograms, pounds, ounces and stone, so typing a tonnage shows the short-ton and pound equivalents together. It doesn’t include the long ton, so for British historical figures multiply by 1.016 to get tonnes. Version 1.0.5 adds a Power category with BTU per hour, watts and kilowatts, which handles air-conditioner sizing once you’ve multiplied the tons by 12,000.
For everyday weights, see kg to lbs. The tonne’s place in the metric system is covered in how the metric system works, and the metric to imperial conversion chart has the other common units.
Frequently asked questions #
Is a tonne the same as a metric ton? #
Yes. Both mean exactly 1,000 kg. “Tonne” is the usual spelling in British and international English, and “metric ton” is the usual US term.
How many pounds are in a ton? #
2,000 lb in a US (short) ton, 2,240 lb in a UK (long) ton, and about 2,204.6 lb in a metric tonne.
Which is heavier, a ton or a tonne? #
A tonne (1,000 kg) is heavier than a US short ton (907 kg) but lighter than a UK long ton (1,016 kg).
How many kg are in a ton? #
A US ton is 907.18 kg, a UK long ton is 1,016.05 kg and a metric tonne is 1,000 kg.
What does “ton” mean for an air conditioner? #
It’s a measure of cooling capacity, not weight. One ton of refrigeration is 12,000 BTU per hour, about 3.52 kW. A 3-ton unit removes 36,000 BTU of heat per hour.