Ton vs tonne: metric, short and long tons explained

A tonne, or metric ton, is exactly 1,000 kg. A US short ton is 2,000 pounds, about 907.2 kg, and a UK long ton is 2,240 pounds, about 1,016 kg. The short ton is about 9% lighter than a tonne; the long ton about 1.6% heavier. When a document just says “ton”, check which one it means before converting.

The three tons side by side

• Tonne (metric ton), t: 1,000 kg = 2,204.6 lb. Used worldwide in science, trade, shipping and most countries’ official statistics.
• Short ton (US ton): 2,000 lb = 907.18 kg. The everyday “ton” in the United States.
• Long ton (imperial ton): 2,240 lb = 1,016.05 kg. The historical British ton, still met in some shipping and older documents.

The Weight Converter lists all three separately, so you can convert between them and kilograms or pounds without guessing.

How big is the difference?

For 50 “tons” of material: 50 tonnes is 50,000 kg; 50 short tons is 45,359 kg; 50 long tons is 50,802 kg. Mixing tonnes and short tons is a 4,641 kg error — about 9.3%. On a delivery, a load limit or a price per ton, that is a real amount of money or a real safety margin. The Percentage Calculator shows the percentage difference between any two figures.

How to tell which ton a document means

• Spelling and symbol. “Tonne” and the symbol “t” always mean 1,000 kg. “Metric ton”, often written MT in trade documents, means the same.
• Origin. US sources usually mean short tons; UK and Commonwealth sources from the last few decades usually mean tonnes, older ones long tons.
• Context. International trade, emissions (“tonnes of CO₂”) and scientific data are almost always metric.
• When in doubt, ask. In a contract or order, write the unit in full — “tonnes (1,000 kg)” — rather than “tons”.

Tons that are not weights

• Refrigeration ton: air conditioners and chillers, especially in the US and India, are rated in tons of cooling. One ton of refrigeration is 12,000 BTU per hour, about 3.5 kW of cooling. A “1.5 ton AC” describes cooling power, not the unit’s weight.
• Register tons: a ship’s gross tonnage historically measured internal volume, with one register ton equal to 100 cubic feet. It says nothing about weight.
• Displacement and deadweight: a ship’s displacement is the weight of water it displaces, and deadweight is how much it can carry; both are stated in tonnes or long tons depending on the source.

For volumes that sound similar, such as cubic metres of water, the Volume Converter helps: a cubic metre of water is 1,000 litres and weighs about one tonne.

Why the tonne is so close to the long ton

The coincidence is not designed. The long ton came from multiples of the pound — 20 hundredweight of 112 lb — while the tonne is simply 1,000 kg, the mass of a cubic metre of water. They land within 1.6% of each other by chance, which is exactly why they get mixed up: the difference is small enough to miss on a single item and large enough to matter on a shipment.

Hundredweight, the other trap

The same split applies one level down. A UK hundredweight (cwt) is 112 lb, a twentieth of a long ton; a US hundredweight is 100 lb, a twentieth of a short ton. Agricultural prices quoted “per cwt” differ by 12% depending on which is meant.

Mistakes to avoid

• Converting a US “ton” at 1,000 kg.
• Reading “1.5 ton” on an air conditioner as its weight.
• Writing “ton” in an international order without saying which.

Checklist

• “Tonne”, “t” or “metric ton”? 1,000 kg.
• US source saying “ton”? Probably 2,000 lb.
• Old British source? Possibly 2,240 lb.
• Cooling capacity or ship tonnage? Not a weight at all.