The catty (斤) and the tael (兩) are still the everyday way to buy meat, vegetables and dried goods in Taiwan, Hong Kong and mainland China, but the word 斤 does not mean the same weight in each place. As the table above shows, a Taiwan catty is 600 g, a Hong Kong catty about 604.8 g and a mainland China jin exactly 500 g. The tael differs even more, because it is 1/16 of a catty in two of those usages and 1/10 in the third.
Where each size comes from
The traditional catty was divided into 16 taels, and two of today’s versions keep that split. In Taiwan, the catty was fixed at 600 g, so a tael is 37.5 g. Taiwan’s Bureau of Standards, Metrology and Inspection lists 1 台斤 as 600 g in its conversion table and classes it as a non-legal unit whose use is discouraged; even so, it remains the unit you will hear at most traditional markets.
Hong Kong defines its catty in law. The Weights and Measures Ordinance (Cap. 68) sets the catty at 0.60478982 kg, very close to 1⅓ avoirdupois pounds, and the tael at 1/16 of that, about 37.80 g. That is why the Hong Kong figures look so precise next to the round Taiwan and mainland numbers. The ordinance keeps the catty and tael as authorised units alongside metric ones. Hong Kong also has a separate tael used for gold, about 37.429 g, which should not be confused with the market tael.
The mainland China jin was redefined in 1959. A State Council scheme renamed the market units so that one kilogram equals two 市斤 and 100 g equals two 市兩, and a related order changed the jin from 16 to 10 liang. The result is a jin of 500 g and a liang of 50 g, easy to convert in your head. The jin stopped being a legal unit for trade after 1990, but it is still how people talk about weight in daily shopping.
How to tell which one a recipe means
Start with where the recipe was written. A recipe from a Taiwan cookbook, blog or cooking show that says 半斤 means 300 g; a mainland China recipe using the same words means 250 g. Recipes in simplified characters usually follow the mainland China jin, while Cantonese recipes from Hong Kong use the Hong Kong catty, often romanised as kan for 斤 and leung for 兩. Many newer recipes in all three places give grams, which avoids the question altogether.
Packaging and price tags help too. Market stalls in Taiwan often price produce and meat per 台斤, so a price tag can tell you which unit a seller means. When a recipe or label is unclear, check whether the numbers divide neatly: amounts like 150 g or 37.5 g hint at the Taiwan system, and 250 g or 50 g at the mainland one.
When the difference matters
For a catty, the gap between Taiwan and Hong Kong is under 1% and can be ignored in cooking. The mainland China jin is another story. Buying 3 catties of pork for a braise means 1,800 g in Taiwan and 1,500 g under the mainland China jin, a difference of 300 g, or about 1,814 g in Hong Kong.
The tael shows the gap most sharply. A recipe asking for 4 兩 of minced pork means 150 g in Taiwan usage, about 151 g in Hong Kong usage and 200 g under the mainland China liang. Follow a mainland recipe with Taiwan taels and you would use a quarter less meat than intended, which changes the balance of a filling or sauce. When in doubt, convert to grams with the mini converter above before you shop.