Tael (ˈteɪl), also known as the tahil and by other names, can refer to any one of several weight measures used in East Asia and Southeast Asia. It usually refers to the Chinese tael, a part of the Chinese system of weights and currency. The Chinese tael was standardized to 50 grams in 1959.
In Hong Kong and Singapore, it is equivalent to 10 mace () or catty, albeit with slightly different metric equivalents in these two places. These Chinese units of measurement are usually used in Chinese herbal medicine stores as well as gold and silver exchange.
The English word tael comes through Portuguese from the Malay word tahil, meaning "weight". Early English forms of the name such as "tay" or "taes" derive from the Portuguese plural of tael, taeis.
Tahil (ˈtɑːhɪl in Singaporean English) is used in Malay and English today when referring to the weight in Malaysia, Singapore, and Brunei, where it is still used in some contexts especially related to the significant Overseas Chinese population.
In Chinese, tael is written (simplified as ) and has the Mandarin pronunciation liǎng. The phrase "half a catty, eight taels" (, bàn jīn, bā liǎng) is still used to mean two options are exactly equivalent, similar to the English "six of one, half-dozen of the other".
In China, there were many different weighting standards of tael depending on the region or type of trade. In general the silver tael weighed around . The most common government measure was the Kuping () tael, weighing . A common commercial weight, the Caoping () tael weighed of marginally less pure silver.
As in China, Japan and Korea used the tael (Japanese: 両; Hepburn: ryō; ) as both a unit of weight and, by extension, a currency.
Traditional Chinese silver sycees and other currencies of fine metals were not denominated or made by a central mint and their value was determined by their weight in taels. They were made by individual silversmiths for local exchange, and as such the shape and amount of extra detail on each ingot were highly variable; square and oval shapes were common but "boat", flower, tortoise and others are known.