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 stablised 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.

Linear Measurements

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.

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

Unit	Kanji	Relative Value	Metric Value	Imperial Value
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(depth)	尋	6 shaku	1.818 m	71.57 in
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.

Volume Measurements

Unit	Kanji	Equivalent Value	Metric Value	Imperial Value
shaku	勺	–	18.039 ml	0.6349 fl oz
gō	合	10 shaku	180.39 ml	6.349 fl oz
shō	升	10 gō	1.8039 l	63.49 fl oz
to	斗	10 shō	18.039 l	3.968 gallons
koku	石	10 to	180.39 litres	39.68 gallons or 4.96 bushels1 man year’s rice.

 Time Measurement (Public)

• sekki 1/12^th of a year (or month)
• chu/setsu 2 week period
• nichi day
• toki Japanese hour
  • jo-koku, or seikoku half-hour preceding the exact hour
  • chu-koku precisely on the hour
  • ge-koku half-hour following the exact hour
• bu 1/10^th Japanese hour
• rin 1/10^th bu, or 1/100^th Japanese hour

Time Measurement (Astronomical)

• ten 5 equal parts of a ko
• ko 5 equal parts dusk to dawn
• koku 1/100th of a Japanese day (or 8 1/3 Public koku)

Time Measurement (Other)

• eto 12 Zodiac animals
• junichi/neto 12 animal hours
• zappou items connected with time

Bell Strike

• 4 Strikes X (1 minute) X X (long) X     through to
• 9 Strikes X (1 minute) X X (long) X X X X X X (10 secs. apart)

Weight (Mass)

• fun 375 grams
• momme 75 grams
• hyakume 375 grams
• kin 600 grams
• kan or kanme 3,750 grams

 

 Currency

At the beginning of the Tokugawa period a decisions was made to create a central currency. The new money was to have gold, silver and copper units – all exchangeable at fixed rates. The Oban and the Koban gold coins were oblong plates, the smaller Ichibukin little rectangular pieces of minted gold. Silver was hardly minted in the European sense of the word. It was traded in lumps and weighed. The central unit for silver, the momme, was (and still is) a mere unit of weight matching 3.75 g. The lowest unit, the copper mon was influenced by the design of Chinese coins, the only object in the ensemble resembling a conventional coin. The rates between gold and silver were fixed, yet market rates fluctuated. The pattern did not change between 1600 and 1700:

Gold:

• 1 oban = 7.5 ryo or koban
• 1 ryo = 4 bu or 4 kan or 70 momme
• 1 bu = 4 shu

Silver:

• 1 kamme = 1000 momme
• 1 momme = 3.75 gram or 10 fun
• 1 fun = 10 rin

Copper:

• 1 kan (1 kg) = 1000 momme