Koku

The kyō-masu (京枡, "Kyoto masu"), the semi-official one shō measuring box since the late 16th century under Daimyo Nobunaga,[17] began to be made in a different (larger) size in the early Edo period, sometime during the 1620s.[18] Its dimensions, given in the traditional Japanese shaku length unit system, were 4 sun 9 bu square times 2 sun 7 bu depth.[lower-alpha 6][18][13] Its volume, which could be calculated by multiplication was:[11]

1 koku = 100 shō = 100 × (49 bu × 49 bu × 27 bu) = 100 × 64,827 cubic bu[18][lower-alpha 7]

Although this was referred to as shin kyō-masu or the "new" measuring cup in its early days,[18] its use supplanted the old measure in most areas in Japan, until the only place still left using the old cup ("edo-masu") was the city of Edo,[19] and the Edo government passed an edict declaring the kyō-masu the official nationwide measure standard[17] in 1669 (Kanbun 9).[19]

When the 1891 Japanese Weights and Measures Act was promulgated, it defined the shō unit as the capacity of the standard kyo-masu of 64827 cubic bu.[15] The same act also defined the shaku length as 10⁄33 metre.[15] The metric equivalent of the modern shō is 2401⁄1331 litres.[20] The modern koku is therefore 240,100⁄1331 litres, or 180.39 litres.[21]

The modern shaku defined here is set to equal the so-called setchū-shaku (setchū-jaku or "compromise shaku"),[22] measuring 302.97 mm, a middle-ground value between two different kane-jaku standards.[lower-alpha 8][23][22] A researcher has pointed out that the (shin) kyō-masu cups ought to have used take-jaku which were 0.2% longer.[12][lower-alpha 9] However, the actual measuring cups in use did not quite attain the take shaku metric, and when the Japanese Ministry of Finance had collected actual samples of masu from the masu-za (measuring-cup guilds) of both eastern and western Japan, they found that the measurements were close to the average of take-jaku and kane-jaku.[28]

The "lumber koku" or "maritime koku" is defined as equal to 10 cubic shaku in the lumber or shipping industry,[29] compared with the standard koku measures 6.48 cubic shaku.[6] A lumber koku is conventionally accepted as equivalent to 120 board feet, but in practice may convert to less.[30] In metric measures 1 lumber koku is about 278.3 litres (61.2 imp gal; 73.5 US gal).

Under the Tokugawa shogunate (1603–1868) of the Edo period of Japanese history, each feudal domain had an assessment of its potential income known as kokudaka (production yield) which in part determined its order of precedence at the Shogunal court. The smallest kokudaka to qualify the fief-holder for the title of daimyō was 10,000 koku (worth ¥705.53 million (2016) (equivalent to ¥719.91 million or US$6.6 million in 2019)[31])[32] and Kaga han, the largest fief (other than that of the shōgun), was called the "million-koku domain". Its holdings totaled around 1,025,000 koku (worth ¥72.3 billion (2016) (equivalent to ¥73.77 billion or US$676.77 million in 2019)[31]). Many samurai, including hatamoto (a high-ranking samurai), received stipends in koku, while a few received salaries instead.

The kokudaka was reported in terms of brown rice (genmai) in most places, with the exception of the land ruled by the Satsuma clan which reported in terms of unhusked or non-winnowed rice (momi (籾).[33] Since this practice had persisted, past Japanese rice production statistics need to be adjusted for comparison with other countries that report production by milled or polished rice.[6]

Even in certain parts of the Tōhoku region or Ezo (Hokkaidō), where rice could not be grown, the economy was still measured in terms of koku, with other crops and produce converted to their equivalent value in terms of rice.[34] The kokudaka was not adjusted from year to year, and thus some fiefs had larger economies than their nominal koku indicated, due to land reclamation and new rice field development, which allowed them to fund development projects.

Koku was also used to measure how much a ship could carry when all its loads were rice. Smaller ships carried 50 koku (7.5 tonnes, 7.4 long tons, 8.3 short tons) while the biggest ships carried over 1,000 koku (150 tonnes, 150 long tons, 170 short tons). The biggest ships were larger than military vessels owned by the shogunate.