How many kilograms are in one tonne?

The tonne is a metric unit of mass equal to 1,000 kilograms. It is commonly referred to as a metric ton in the United States. It is equivalent to approximately 2,204.6 pounds; 1.102 short tons (US) and 0.984 long tons (UK).

Before metrication in the UK, the unit used for most purposes was the Imperial ton of 2,240 pounds avoirdupois or 20 hundredweight (usually referred to as the long ton in the US), equivalent to approximately 1,016 kg, differing by about 1.6% from the tonne. The UK Weights and Measures Act 1985 explicitly excluded from use for trade certain imperial units, including the ton, unless the item being sold or the weighing equipment being used was weighed or certified prior to 1 December 1980, and even then only if the buyer was made aware that the weight of the item was measured in imperial units.

Ton and tonne are both derived from a Germanic word in general use in the North Sea area since the Middle Ages to designate a large cask, or tun. A full tun, standing about a meter high, could easily weigh a tonne. An English tun (an old wine cask volume measurement equivalent to approximately 954 liters) of wine has a relative mass of approximately 954 kg if full of pure water, a little less for wine.