In both systems, there are twenty hundredweights to a ton – the long ton of 2240 pounds (approximately equal to a metric tonne), and the short ton of 2000 pounds. In both systems, the hundredweight is abbreviated cwt, where wt is an abbreviation for weight and c is an abbreviation for one hundred (since the Roman numeral C is equal to 100).
Prior to the 15th century in England, a hundredweight used the old hundred of 108 lb, giving a ton of 2160 pounds. In some industries (notably forges) this old hundred was retained somewhat longer. The London hundredweight of 112 pounds eventually replaced the old hundred.
The short hundredweight is commonly used in the sale of livestock and some cereal grains and oilseeds and on futures exchanges. The long hundredweight is now little used in any country, except sometimes for measuring the bells used for change ringing.