Japanese units of measurement

Shakkan-hō (尺貫法) is the traditional Japanese system of measurement. The name shakkanhō originates from the name of two of the units, the shaku, a unit of length, and the kan, a mass measurement.

The system is Chinese in origin. The units originated in the Shang Dynasty in the 13th century BC, and eventually stabilized in the Zhou Dynasty in the 10th century BC and spread from there to Japan, South East Asia, and Korea. The units of the Tang Dynasty were officially adopted in Japan in 701, and the current shaku measurement has hardly altered since then. Many Taiwanese units of measurement are derived from the shakkanhō system.

From 1924, the shakkanhō system was replaced by the metric system,[1] and use of the old units for official purposes was forbidden after 31 March 1966.[2] However, in several instances the old system is still used. In carpentry and agriculture use of the old-fashioned terms is common. Tools such as Japanese chisels, spatels, saws, hammers are manufactured in sizes of sun and bu. Land is sold on the basis of price in tsubo. Until the 2005 Japanese census, people were able to give the area of their houses in either square metres or tsubo. The tsubo was not used in the 2010 census.

There are several different versions of the shakkanhō. The tables below show the one in common use in the Edo period. In 1891 the most common units were given definitions in terms of the metric system:

1891 definitions
Unit Definition Conversions
Romanized Kanji
Length metres metres inches feet yards
10033 3.03 119.3 9.942 3.314
kanejaku 曲尺 1033 0.303 11.93 0.9942 0.3314
Volume litres litres millilitres US
fluid ounces
fluid ounces
shō 24011331 1.804 1804 61.00 63.49
Mass grams grams drams ounces pounds
momme 154 3.75 2.116 0.1323 0.008267
Note: Definitions are exact and conversions are rounded to four significant figures.


The basis of the shakkanhō length measurements is the shaku, which originated in ancient China. The other units are all fixed fractions or multiples of this basic unit. The shaku was originally the length from the thumb to the middle finger (about 18 cm or 7.1 in), but its length, and hence the length of the other units, gradually increased, since the length of the unit was related to the level of taxation.

Various shaku developed for various purposes. The unit of all measurement, such as area, is shaku. To distinguish from other shaku, this unit is called the kanejaku (曲尺). Kanejaku means "carpenter's square", and this shaku was used by Japanese carpenters. The carpenter's shaku, used for construction, preserved the original Chinese shaku measurement, because it was never altered, whereas the other shaku systems, which were used for taxation or trade, were altered to increase taxation, and, hence, gradually deviated from the original value.

The kujirajaku (鯨尺), literally "whale shaku", was a standard used in the clothing industry. The name, "whale shaku", comes from the rulers, which were made from baleen. A kujirajaku is 25% longer than kanejaku.

As well as the kanejaku and kujirajaku systems, other shaku systems also existed. One example is the gofukujaku (呉服尺), which refers to traditional Japanese clothing, such as kimonos. In the gofukujaku system, one shaku equals 1.2 times the kanejaku.

Shaku units are still used for construction materials in Japan. For example, plywood is usually manufactured in 182 cm × 91 cm (about 72 in × 36 in) sheets known in the trade as saburokuhan (3 × 6版), or 3 × 6 shaku. Each sheet is about the size of one tatami mat. The thicknesses of the sheets, however, are usually measured in millimetres.

The names of these units also live in the name of the bamboo flute shakuhachi (尺八), literally "shaku eight", which measures one shaku and eight sun, and the Japanese version of the Tom Thumb story, Issun Bōshi (一寸法師), literally "one sun boy", as well as in many Japanese proverbs.

The Shōsōin in Nara has ivory one-shaku rulers, the kōgebachiru-no-shaku (紅牙撥鏤尺).

Table of Lengths
Unit shaku Metric Imperial/US
Romanized Kanji millimetres metres inches feet yards
毛, 毫  110000  0.03030 3.030×105 1.193×103 9.942×105 3.314×105
rin 11000  0.3030 3.030×104 0.01193 9.942×104 3.314×104
bu 1100  3.030 3.030×103 0.1193 9.942×103 3.314×103
sun 110  30.30 0.03030 1.193 0.09942 0.03314
shaku 1  303.0 0.3030 11.93 0.9942 0.3314
ken 6  1818 1.818 71.58 5.965 1.988
hiro 6  1818 1.818 71.58 5.965 1.988
10  3030 3.030 119.3 9.942 3.314
chō 360  1.091×105 109.1 4295 357.9 119.3
ri 12,960  3.927×106 3927 1.546×105 1.288×104 4295
  • Conversions to metric, imperial and US customary units are rounded to four significant figures.
  • The smallest units, , rin and bu, are actually the names of fractions, 110000, 11000 and 1100, respectively, which are also used as fractional units.
  • The shaku is, in some cases, the Japanese equivalent to the foot.[3]
  • The hiro is a unit of depththe Japanese equivalent of the fathom.
  • 1 chō = 60 ken ˜ 0.1091 kilometres ˜ 0.06779 miles
  • 1 ri = 36 chō ˜ 3.927 kilometres ˜2.440 miles

Note: There is an older type of 'ri', about 600 m. This can be seen in use, for example, in beach names. Kujukuri Beach is 99 ri (kyu ju ku), about 60 km. Shichiri Beach is 7 ri (shichi) 4.2 km. While this use is evidence of the existence of the 'old' ri, information about it in English is hard to come by.


The tsubo, which is essentially the area of two standard sized tatami mats (tatami have an aspect ratio of 2:1, so two side by side form a square), is still commonly used in discussing land pricing in Japan. Note that actual tatami vary in size regionally, though legally the area of a tsubo is standardized. The larger units are also commonly used by Japanese farmers for discussing the sizes of fields.

Table of area units
Unit tsubo Metric Imperial/US
Romanized Kanji square
shaku 1100 0.03306 51.24 0.3558 0.03954
110 0.3306 512.4 3.558 0.3954
12 1.653 2562 17.79 1.979
tsubo 1 3.306 5124  35.58 3.954
bu 1 3.306 5124  35.58 3.954
se 30 99.17 1.537×105 1067  118.6
tan 段, 反 300 991.7 1.537×106 1.067×104 1186
chō[4] 町, 町歩 3000 9917  1.537×107 1.067×105 1.186×104
  • Conversions to metric, imperial and US customary units are rounded to four significant figures.
  • A is the size of one tatami mat-used in quoting room sizes.
  • 1 tsubo = 1 square ken-used in construction.
  • 1 bu = 1 square ken-used in agriculture.
  • 1 tan ≈ 0.09917 hectares ≈ 0.2451 acres
  • 1 chō ≈ 0.9917 hectares ≈ 2.451 acres


A sake cup (1 ) for celebrations

These units are still used, for example, in sake production.

Table of volume units
Unit shō Metric US liquid measure Imperial
Romanized Kanji millilitres litres fluid ounces pints gallons fluid ounces pint gallons
sai 11000 1.804 1.804×103 0.06100 3.812×103 4.765×104 0.06349 3.174×103 3.968×104
shaku 1100 18.04 0.01804 0.6100 0.03812 4.765×103 0.6349 0.03174 3.968×103
110 180.4 0.1804 6.100 0.3812 0.04765 6.349 0.3174 0.03968
shō 1 1804 1.804 61.00 3.812 0.4765 63.49 3.174 0.3968
to 10 1.804×104 18.04 610.0 38.12 4.765 634.9 31.74 3.968
koku 100 1.804×105 180.4 6100 381.2 47.65 6349 317.4 39.68
  • Conversions to metric, imperial and US customary units are rounded to four significant figures.
  • The is a common size for serving sake.
  • The shō (about 64.827 cubic sun) is a former common sake-bottle size (it is presently legally filled and labelled as 1800 mL).
  • The koku (about 40.95 US dry gal) originally was the volume of rice a person would eat in one year.


The Japanese unit of mass, momme, is a recognized unit in the international pearl industry.

Table of units of mass
Unit momme Metric Avoirdupois
Romanized Kanji milligrams grams kilograms drams ounces pounds
fun 110 375 0.375 3.75×104 0.2116 0.01323 8.267×104
momme 1 3750 3.75 3.75×103 2.116 0.1323 8.267×103
hyakume 百目 100 3.75×105 375 0.375 211.6 13.23 0.8267
kin 160 6×105 600 0.6 338.6 21.16 1.323
kan or kanme 貫, 貫目 1000 3.75×106 3750 3.75 2116 132.3 8.267
  • Metric values are exact and conversions to avoirdupois units are rounded to four significant figures.
  • Momme is the usual form, but strictly speaking the current romanization system dictates monme.


The names of old money live on in Japanese proverbs such as haya oki wa san mon no toku, literally "Waking early gets you three mon", comparable to the English language proverb, "Early to bed, early to rise makes a man healthy, wealthy, and wise."

Table of money units
Unit Equivalent to
Romanized Kanji
1 mon  
1 hiki 10 mon
1 kanmon 貫文 100 hiki

Other units

Apart from shakkanhō and the metric system, other units are also commonly used in Japan. For example, the inch is used in the following:

See also


  1. "改正度量衡法規". National Diet Library. Retrieved 7 July 2010.
  2. "メートル条約". International Metrology Cooperation Office. Retrieved 7 July 2010.
  3. Ministry of Railway (鉄道省 Tetsudō-shō) ([大正10]). Nippon (or Nihon) Tetsudō-shi 日本鉄道史 [Japan Railway History] (in Japanese). 1 of 3 (上巻 Jōkan). [Tokyo] : [Ministry of Railway]. p. 49. Check date values in: |date= (help) "In the 10th month of Meiji 3, probably November 1871, we defined 1 English foot of railway as 1 shaku 4 rin (1.004 shaku) of ours."
  4. "Chōbu" is used when no fraction follows

External links

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