hundredweight

The hundredweight was originally 100 pounds in England — its name was literal. In medieval English trade, the unit was straightforward: one hundred pounds of wool, one hundred pounds of iron, one hundred pounds of salt. But somewhere around the fourteenth century, English merchants began using a 112-pound hundredweight instead. The reason was mathematical: 112 divides into neat fractions. A quarter of 112 is 28 (a stone of two). An eighth is 14 (a stone). The number 112 fit the stone-and-pound system better than 100 did.

The 112-pound hundredweight became the British standard by the sixteenth century. Twenty hundredweight made a ton — and twenty times 112 is 2,240 pounds, the long ton. When Parliament codified the Imperial system in 1824, the hundredweight was officially 112 pounds, or eight stone. The word 'hundredweight' had been mismatched with its own meaning for at least four centuries.

The United States never adopted the 112-pound version. The American hundredweight is 100 pounds — the short hundredweight, abbreviated cwt. (The 'c' is the Roman numeral for 100, and 'wt' is weight.) Twenty American hundredweight make a short ton of 2,000 pounds. The two systems ran in parallel throughout the nineteenth and twentieth centuries, creating confusion in transatlantic trade that metrication was supposed to resolve.

The hundredweight is nearly extinct. The metric tonne has replaced it in most international trade. But it persists in American agriculture — cattle are priced per hundredweight, and grain elevator receipts still show cwt. A word that means 'one hundred' but equals 112 in one country and 100 in another, measuring a quantity that neither number explains. The name was wrong before it crossed the ocean.