sci.lang.japan FAQ / 12. Numbers, counting, and dates

12.7. What are the old Japanese units like shaku?

The Shakkanhō (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 unit of weight.

This system of units originated in China in the 13th century BC, and stablized in the 10th century BC. The units spread from China to Japan, South East Asia, and Korea. The units were adopted in Japan in 701.

In 1924, the shakkanhō system was replaced by the metric system, and the old units were forbidden for official purposes after 31 March 1966. However, the old system is still used. In carpentry and agriculture, use of the old fashioned terms is common. Japanese chisels are manufactured in sizes of sun and bu. Japanese bathrooms are built in sizes which are fractions of a tsubo, usually either 3/4, 1, or 1 1/4 of a tsubo and land is sold on the basis of price in tsubo.

There are several different versions of the shakkanhō. The tables below give the one in common use in the Edo period.

Length

See also the FAQ's length converter.

The basis of length measurements is the shaku. The other units are fractions or multiples of it.

Various different shaku developed for various purposes. The unit now most widely recognized as a shaku in Japan is the kanejaku (曲尺), shaku, the system shown in the table below. Kanejaku means "carpenter's square", and this shaku is the one used by Japanese carpenters.

The kujirajaku (鯨尺), literally "whale shaku", was a standard used in the clothing industry. The name "whale shaku" comes from the measuring rulers used, which were made from baleen. A kujirajaku is 1 1/4 the length of a kanejaku.

As well as the kanejaku and kujirajaku system, various other shaku systems also exist, for example the gofukujaku (呉服尺), where gofuku means traditional Japanese clothes, such as kimonos. In this system, one shaku is 1.2 what it is in the kanejaku system.

In 1891, the lengths of the two most common shaku were defined in terms of the metric system:

1891 definitions Kanji Metric value Imperial equivalent
1 kanejaku 曲尺 10/33 m 11.93 in
1 kujirajaku 鯨尺 25/66 m 14.9 in

The names of these units also live on in the name of the bamboo flute shakuhachi (尺八), literally "shaku eight", which is one shaku and eight sun in length, and the Japanese story Issun Bōshi (一寸法師), literally "one sun boy".

Unit	Kanji	Relative value	Metric value	Imperial value	Notes
mō	毛, 毫	1/1000 sun	0.03030 mm	0.001193 in
rin	厘	1/100 sun	0.3030 mm	0.01193 in
bu	分	1/10 sun	3.030 mm	0.1193 in
sun	寸	10 bu, 1/10 shaku	3.030 cm	1.193 in
shaku	尺	10 sun	30.30 cm	11.93 in
ken	間	6 shaku	1.818 m	71.57 in
hiro	尋	6 shaku	1.818 m	71.57 in	A unit of depth
jō	丈	10 shaku	3.030 m	119.3 in
chō	町	60 ken	109 m	358 ft
ri	里	36 chō	3.927 km	2.44 miles

The smallest units, mō, rin, and bu, are actually the names of fractions, 1/1000, 1/100, and 1/10, respectively, which are also used as fractional units.

Area

Volume

Weight

Other units

Apart from shakkanhō and the metric system, other units are also commonly used in Japan. The most common unit found is the inch. Inches are used

for Japanese bicycles, which are based on a British system; the tyre sizes are measured in inches rather than centimetres;
in the electronics industry for the sizes of parts, connectors, semiconductor wafers, and magnetic tape;
for the sizes of television screens and monitors; (Because inches are not a legally recognized unit in Japan, instead of writing the word "inch", Japanese companies substitute "-gata" (型). Thus, a television with a 17 in diagonal measure is described as 17型.)
for the sizes of photographic prints, though rounded to the nearest millimetre.

sci.lang.japan FAQ / 12. Numbers, counting, and dates

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