Sào, Lượng, Tsubo and Jin: A Practical Guide to East Asian Traditional Units

Vietnam, China, Japan and Korea all use the metric system officially. Yet if you buy land in the Red River Delta, gold in Ho Chi Minh City, an apartment in Tokyo or pork at a market in Seoul, you will still meet units that predate the meter: sào, mẫu, lượng, chỉ, 斤, 坪, 평, 돈. These units appear in land records, price boards and everyday conversation, so developers building apps for these markets need to handle them correctly.

This guide lists the exact values, explains where the regional differences come from and shows a few connections between countries that are easy to miss.

#Vietnam: land area

Land in rural Vietnam is still commonly described in sào and mẫu (1 mẫu = 10 sào). The catch is that the size of a sào depends on the region:

In the Mekong Delta and the south, people usually speak of a công. The most common value is 1,000 m² (sometimes called "công tầm nhỏ"), but some areas use a larger công of 1,296 m² ("công tầm lớn"). When a document or a seller mentions sào, mẫu or công, always ask which region's definition applies, or better, look for the area in square meters on the land-use certificate.

A quick sanity check: a 1-sào plot in Hanoi (360 m²) is only about 72% of a 1-sào plot in Hue or Quang Nam (≈ 500 m²). On a price per sào, that difference matters.

#Vietnam: gold and everyday weight

Gold prices in Vietnam are quoted per lượng (also called cây):

• 1 lượng = 10 chỉ = 37.5 g
• 1 chỉ = 10 phân = 3.75 g

So a 2-chỉ ring weighs 7.5 g, and "5 cây vàng" is 187.5 g of gold. Purity is a separate label: "vàng 9999" or "vàng bốn số 9" means 99.99% gold, while jewelry gold is often 75% (18K) or 61% (14.6K).

For everyday goods the modern units are simply multiples of the kilogram: 1 yến = 10 kg, 1 tạ = 100 kg, 1 tấn = 1,000 kg. In markets, "một cân" today means 1 kg and "một lạng" means 100 g. Historically a cân was about 0.6 kg and a lạng about 37.8 g, which is why older texts can be confusing.

#China: jin and liang

Mainland China standardized its market units ("市制") so that they fit neatly with the metric system:

• 1 市斤 (jin) = 500 g
• 1 市两 (liang) = 50 g, and 10 liang = 1 jin
• 1 市尺 (chi) = 1/3 m ≈ 33.3 cm

Before this reform a jin had 16 liang, and that older system survives elsewhere. In Taiwan, 1 台斤 = 600 g and is divided into 16 台两 of 37.5 g each, exactly the same as a Vietnamese lượng. Hong Kong uses a slightly different jin of about 604.8 g.

#Japan: tsubo, shaku, monme

Japan replaced its traditional system (尺貫法, shakkanhō) with the metric system for official and commercial use in the mid-20th century, but some units stay alive informally:

• 坪 (tsubo) = 400/121 m² ≈ 3.306 m², roughly the area of two tatami mats. Apartment and shop sizes are still often advertised in tsubo.
• 尺 (shaku) = 10/33 m ≈ 30.3 cm, still used by carpenters and in traditional crafts.
• 貫 (kan) = 3.75 kg and 匁 (monme) = 3.75 g. Pearls are traded internationally by the "momme".

#Korea: pyeong, geun, don

Korea uses the same land unit as Japan under a different name: 평 (pyeong) ≈ 3.306 m². In July 2007 the government removed it from lawful commercial use and required square meters, but enforcement was later relaxed, and pyeong is still the unit most people use when they describe an apartment, such as "30평" (about 99 m²).

• 근 (geun) is commonly 600 g for meat and 375 g for fruit and vegetables, so "한 근" depends on what you are buying.
• 돈 (don) = 3.75 g and is the standard unit for gold jewelry, such as a "한 돈" baby ring.

#The hidden connection: 3.75 grams

Put the numbers side by side and a pattern appears:

All of them descend from the old Chinese weight system based on the tael (两), and when each country fixed its units to the metric system, many of them landed on the same round value of 3.75 g. Even the land units are related: the Japanese tsubo and Korean pyeong are the same unit, defined as a square of 6 shaku per side.

#Tips for developers

1. Store metric, display local. Keep square meters and grams in your database and convert only for display. Traditional units are ambiguous by region and should never be the source of truth.
2. Make the region explicit. If your app shows sào or mẫu, label them "sào (Bắc Bộ)" or "sào (Trung Bộ)" rather than just "sào".
3. Separate weight and purity for gold. A price "per lượng" only makes sense together with the purity (9999, 18K…).
4. Use exact factors. 1 tsubo is 400/121 m², not "3.3 m²". Rounding errors add up quickly on large areas.

#Conclusion

Traditional units are not going away in land and gold markets, and they are easy to get wrong because the same name can mean different values by region or by product. Keep the metric value as your reference, label regional units clearly and use exact conversion factors.

Our Unit Converter includes all the units in this article, including sào and mẫu for each region, lượng and chỉ, jin, liang, tsubo and pyeong, next to more than 140 standard units. Everything runs locally in your browser.