The hundredweight or centum weight (abbreviated cwt) is a unit of mass defined in terms of the pound (lb). The definition used in Britain differs from that used in North America. The two are distinguished by the terms long hundredweight and short hundredweight:
Under both conventions, there are twenty hundredweight in a ton, the long ton being 2,240 lb and the short ton being 2,000 lb.
The long and short hundredweight are both descended from the French avoirdupois weight system, which became established in England in Late Medieval times. British custom came to widely use the stone weight, which is 14 pounds, and wished for the hundredweight to be a whole number of stones (and 100 is not a multiple of 14). The stone was not one of the avoirdupois units in Medieval France, and never became customary in the British American colonies or the USA. In 1824 in the UK, new weights and measures legislation made it illegal for merchants to use the word hundredweight in the sense of a hundred pounds. A merchant could be sued for fraud for doing so. In 1879, the hundred pound weight was re-legalized for trade in the UK under the name "cental", in response to legislative pressure from UK merchants who were importing corn and tobacco from the USA.[3]
The short hundredweight is commonly used in USA in the sale of livestock and some cereal grains[4] and oilseeds, paper, and concrete additives and on some commodities in futures exchanges[5] A few decades ago, commodities weighed in terms of long hundredweight included cattle, cattle fodder, fertilizers, coal, some industrial chemicals, other industrial materials, and so on, but since the adoption of the metric system by all English-speaking countries apart from the USA, it is now hardly used other than by church bell ringers[6] but church bell manufacturers are increasingly moving over to the metric system.[7] Before the 15th century in England, a hundredweight was a different unit equal to 108 lb.[8]