Long ton, short ton and metric tonne
Three different tons travel on the same cargo documents. The metric tonne is 1000 kg, the long ton (British) is 2240 lb, that is 1016.05 kg, and the short ton (American) is 2000 lb, that is 907.18 kg. The difference between the first two is small, about 1.6%, and that is exactly what makes it dangerous on a big parcel of cargo.
Quick try:
The long ton (British, 2240 lb) and the short ton (American, 2000 lb) are not the metric tonne. Gross and net tonnage (GT, NT) are missing here on purpose: they are not mass.
Metric tonnes converted
| t | LT | ST | lb |
|---|---|---|---|
| 1 | 0.9842065 | 1.102311 | 2,204.623 |
| 2 | 1.968413 | 2.204623 | 4,409.245 |
| 5 | 4.921033 | 5.511557 | 11,023.11 |
| 10 | 9.842065 | 11.02311 | 22,046.23 |
| 100 | 98.42065 | 110.2311 | 220,462.3 |
| 1,000 | 984.2065 | 1,102.311 | 2,204,623 |
| 10,000 | 9,842.065 | 11,023.11 | 22,046,230 |
Values computed from the exact definitions of the units (NIST SP 811 and the international agreements), rounded to 7 significant digits. The first column is metric tonnes.
Which ton do the papers mean
Modern cargo documents, bunker delivery notes and deadweight figures are in metric tonnes, usually written MT or t. The long ton survives in older ships documentation and in warship displacement, the short ton mainly in American domestic trade. If a figure is written just "tons", find out which one before you plan the loading.
Gross tonnage (GT) and net tonnage (NT) are not on this list on purpose. They are not mass and not volume: they are dimensionless results of a formula from the Tonnage Convention, and any calculator that converts them into tonnes is misleading you.
Frequent questions
How many kilograms is a long ton?
Exactly 1016.0469088 kg, that is 2240 pounds. It is about 1.6% heavier than a metric tonne.
What is the difference between a long ton and a short ton?
A long ton is 2240 lb (1016.05 kg), a short ton is 2000 lb (907.18 kg). The short ton is about 10% lighter, so on a 10,000 ton parcel the gap is more than a thousand tonnes.
Is deadweight in metric tonnes or long tons?
Modern deadweight (DWT) is given in metric tonnes. Older ships papers and some American sources use long tons, and the abbreviation DWT alone does not tell you which, so check the ship documents.
Can gross tonnage be converted into tonnes?
No. Gross tonnage is a measure of enclosed volume calculated by a formula, not a weight. A ship of 3000 GT does not weigh 3000 tonnes, and there is no honest conversion between the two.