Short ton, metric ton, long ton: why “tons” on a packing list is ambiguous
The short answer
“Tons” on its own can mean a short ton of 2,000 pounds, a metric ton of 1,000 kilograms or a long ton of 2,240 pounds, so 5.64 tons is 5,117 kg, 5,640 kg or 5,731 kg. Don’t compare it with a weight in kilograms until the shipper says which ton they mean.
Last checked By Muhammad Saadullah Khan, Founder
Three tons, one word
NIST Handbook 44, from the US National Institute of Standards and Technology, says it plainly: “the words ‘ton’ and ‘tonnage’ are used in widely different senses, and a great deal of confusion has arisen regarding the application of these terms.” As a unit of mass it lists three: “the short, or net ton of 2 000 pounds”, “the long, gross, or shipper’s ton of 2 240 pounds” and “the metric ton of 1 000 kilograms”.
| Ton | Also called | Defined as | In kilograms |
|---|---|---|---|
| Short ton | Net ton | 2,000 pounds | 907.18474 kg |
| Metric ton | Tonne | 1,000 kilograms | 1,000 kg |
| Long ton | Gross or shipper’s ton | 2,240 pounds | 1,016.0469088 kg |
The kilogram values are exact, because the pound is defined in kilograms: “1 avoirdupois pound = 0.453 592 37 kilogram”, in Handbook 44. Its conversion tables give 907.184 74 kg for the short ton and 1 016.046 908 8 kg for the long ton.
UK law uses the same definitions. Schedule 1 of the Weights and Measures Act 1985 gives “Ton = 2240 pounds” and “Tonne, metric tonne = 1000 kilograms”, and defines the pound as 0.453 592 37 kilogram. It puts the 2,240-pound ton among “certain units which may not be used for trade except as supplementary indications”.
Which ton a document probably means
Handbook 44 describes the habits: “In the United States and Canada the ton (mass) most commonly used is the short ton. In Great Britain, it is the long ton, and in countries using the metric system, it is the metric ton.”
For freight it is more specific. Cargo tonnage, it says, “refers to the weight of the particular items making up the cargo. In overseas traffic it is usually expressed in long tons of 2 240 pounds or metric tons of 2 204.6 pounds. The short ton is only occasionally used.”
US rules allow either system on an import invoice. 19 CFR 141.86(a)(4) asks for quantities “in the weights and measures of the country or place from which the merchandise is shipped, or in the weights and measures of the United States”. So a US-bound invoice may state its weights in either, and the packing list may not use the same one.
“Probably” is the problem. These are habits, not rules, and a document check can’t run on probably. A shipper in a metric country may still write tons for a buyer in the US, and a form may carry a unit from wherever it was first drawn up.
How much it matters
The gap grows with the weight. Computed from the definitions above and rounded to the kilogram:
| Tons on the document | As short tons | As metric tons | As long tons | Long minus short |
|---|---|---|---|---|
| 1 ton | 907 kg | 1,000 kg | 1,016 kg | 109 kg |
| 5.64 tons | 5,117 kg | 5,640 kg | 5,731 kg | 614 kg |
| 10 tons | 9,072 kg | 10,000 kg | 10,160 kg | 1,089 kg |
| 25 tons | 22,680 kg | 25,000 kg | 25,401 kg | 2,722 kg |
On 5.64 tons, the short and long readings are 614 kg apart. Against an invoice that says 5,640.00 kg, the metric reading agrees exactly, the short reading is 523 kg under and the long reading 91 kg over. One of the three is a match, and the document doesn’t say which.
Convert a weight
Enter the number of tons printed on the document to see it as each kind of ton, in kilograms. It starts at the sample’s value. Use a point for decimals, 5.64 rather than 5,64: a comma can be a decimal mark or a thousands separator, and the converter won’t guess which one you meant.
- As short tons
- 5,117 kg
- As metric tons
- 5,640 kg
- As long tons
- 5,731 kg
1 short ton = 907.18474 kg, 1 metric ton = 1,000 kg, 1 long ton = 1,016.0469088 kg. Rounded to the kilogram.
What to ask the shipper for
- Kilograms on both documents. It is the one unit both can share with no conversion at all.
- Or the ton written out. “Metric tons”, “short tons” or “long tons” leaves nothing to guess. Handbook 44’s tables use the symbol “t” for the metric ton, and the UK Act names it the tonne.
- The same unit on the commercial invoice and the packing list, for gross weight and for net weight.
- Which weight it is. Gross weight includes the packaging and net weight does not. If the documents give both, each needs its own unit.
Pounds are not ambiguous in the same way. The avoirdupois pound is exactly 0.453 592 37 kilogram in both Handbook 44 and the UK Act, so a weight in pounds converts without a question.
One more trap: on shipping documents a ton can be a volume. Handbook 44 lists “the register ton of 100 cubic feet” and “the measurement ton of 40 cubic feet”, capacity units “used in expressing the tonnage of ships”. If tons appear next to a volume, ask what was measured.
For the rest of the check, see how to check a packing list against a commercial invoice, and which fields must match for the other fields.
Checking this automatically
FlowDocs never picks a ton for you. A gross weight printed in “tons” comes back Cannot compare, with the reason and the value as printed. Gross weight is compared only when both documents state it in kilograms; any other unit returns Cannot compare instead of a converted guess.
The commercial invoice and packing list checker lists every rule FlowDocs applies.