The old units you still meet in Japan

Japan used its own system of units for centuries. It is called shakkanhō, after its basic units for length and weight: the shaku and the kan. Japan moved to the metric system in the twentieth century, and the old units are no longer legal for trade or certification. Article 8 of the Measurement Act says that units outside the legal ones may not be used for transactions or certificates.

In daily life, several of them are still around. Real estate agents talk about a plot in tsubo. Rice is measured and cooked by the gō. A house is described in ken, and a tatami room is counted in mats. If you read an old floor plan, listen to an older relative, or use a Japanese rice cooker, you will need to convert them.

The conversion chart

This chart shows what one of each main unit is in metric. The values come from three fixed definitions: one shaku is 10/33 of a meter, one kan is 3.75 kilograms, and one shō is 2401/1331 of a liter.

The values match the conversion table in the Chiba Prefecture statistical yearbook. One meter is 3.3 shaku, one square meter is 0.3025 tsubo, one liter is 0.55435 shō, and one kilogram is 266.667 monme.

How to use the converter

Choose length, area, volume or weight. Enter a number and choose the unit. The page shows the same amount in every unit of that type. If you enter a traditional unit, you see the metric value in the headline. If you enter a metric unit, you see the shaku, tsubo, shō or kan value. Values are shown to six significant digits.

Length: shaku, ken and chō

A shaku is about 30.3 cm, a little less than a foot (30.48 cm). A sun is a tenth of a shaku, about 3.03 cm. A ken is six shaku, about 1.82 meters. It is the spacing of pillars in a traditional house. A chō is 60 ken, about 109 meters, and a ri is 36 chō, about 3.93 kilometers. A person who is 170 cm tall is about 5.61 shaku, or 5 shaku and 6 sun.

Area: tsubo, se and tan

A tsubo is a square one ken on each side, which is 400/121 square meters, or about 3.306 square meters. Property is still often described in tsubo. A se is 30 tsubo, a tan is 10 se, which is 300 tsubo, and a chōbu is 10 tan, which is 3,000 tsubo. A tan is about 991.7 square meters, close to 10 ares, and rice fields are still often described this way.

A tsubo is often said to be about two tatami mats, but tatami sizes differ by region, so the match is not exact. For rooms, use the tatami room size calculator, which converts mats, square meters and tsubo with the regional mat sizes. To read a listing, see how to read a Japanese apartment floor plan.

Volume: gō, shō and koku

A shō is about 1.804 liters. A gō is a tenth of that, about 180.4 milliliters. A to is 10 shō, about 18.04 liters, and a koku is 100 shō, about 180.4 liters. One liter is about 0.554 shō. The gō is the unit you will meet most often, because it is the unit of rice.

Weight: monme and kan

A kan is 3.75 kilograms, and a monme is one thousandth of a kan, which is 3.75 grams. One kilogram is about 266.7 monme.

The rice cooker cup

If you buy a Japanese rice cooker, it comes with a small plastic cup. That cup holds 180 milliliters, which is one gō. The Ministry of Agriculture, Forestry and Fisheries explains that you should measure rice with this cup, heaped and then leveled off. The inner pot has water lines marked in gō, so two cups of rice means filling the water to the line marked 2.

A cup of rice does not weigh a cup of water. The Ministry gives one gō of polished rice as 150 grams, and says it becomes about 340 grams of cooked rice. That is 2.2 to 2.3 times the raw weight. The weight varies with the kind of rice, new or old crop, and moisture, so treat 150 grams as a guide. The box above works out the volume, the raw weight and the cooked weight for any number of gō.

Do not use a normal measuring cup in place of the rice cup. Japanese kitchen measuring cups are often 200 milliliters, and the US customary cup is about 237 milliliters. Both are larger than the rice cooker cup, so you would put in too much rice for the water lines.

What these numbers leave out

• The traditional units are exact definitions. Everyday use is rougher: a plot sold as 50 tsubo may be a rounded size.
• Rice weight is a guide. Brown rice, rinse-free rice and different crops differ a little.
• In Japan, trade and certificates must use the legal metric units. Use these values to understand a number, not to fill in a form.

Frequently asked questions

How many centimeters is one shaku?

About 30.3 cm. A shaku is exactly 10/33 of a meter, so one meter is 3.3 shaku. A sun is a tenth of a shaku, about 3.03 cm.

How many square meters is one tsubo?

About 3.306 square meters. A tsubo is a square one ken (six shaku) on each side, which is exactly 400/121 square meters. It is roughly two tatami mats, but mat sizes differ by region.

How much is one gō of rice?

One gō is 180 milliliters, the size of the cup that comes with a rice cooker. It holds about 150 grams of polished rice, which cooks to about 340 grams.

How many liters is one shō?

About 1.804 liters. A gō is a tenth of that, about 180.4 milliliters. A koku is 100 shō, about 180.4 liters.

How many kilograms is one kan?

3.75 kilograms. A monme is a thousandth of a kan, which is 3.75 grams.

Sources

• Chiba Prefecture: statistical yearbook, table of weights and measures, 2025 edition (in Japanese)
• Measurement Act, Article 8: units other than the legal units may not be used for trade or certification (e-Gov, in Japanese)
• Ministry of Agriculture, Forestry and Fisheries: weight of rice and cooked rice, one gō of rice is 150 g and cooks to about 340 g (in Japanese)
• Ministry of Agriculture, Forestry and Fisheries, Kinki regional bureau: how to cook rice in a rice cooker, with the 180 mL cup (in Japanese)
• One shō = 2401/1331 liters follows from one shaku = 10/33 meter. It matches the Chiba table.

Related pages

• Tatami room size calculatorJō to square meters and square feet, with the four regional mat sizes.
• How to read a Japanese floor plan1K, 1LDK, jō and m²: what the codes and numbers in a rental listing mean.
• Japanese paper and envelope sizesA4, JIS B5, envelope numbers and the size limits for postcards and letters.
• Emergency supplies calculator for JapanHow much water, food and toilet supplies to stock at home, from Japanese government guidelines.
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• Japanese era names explainedHow gengō are set, how Heisei and Reiwa began, and how to convert era years.

Last updated: 2026-10-04