The amount of rice production measured in koku was the metric by which the magnitude of a feudal domain (han) was evaluated.
[4] As a rule of thumb, one koku was considered a sufficient quantity of rice to feed one person for one year.
[5][b][c] The Chinese equivalent or cognate unit for capacity is the shi or dan (Chinese: 石; pinyin: shí, dàn; Wade–Giles: shih, tan) also known as hu (斛; hú; hu), now approximately 103 litres but historically about 59.44 litres (13.07 imp gal; 15.70 US gal).
[16] 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.
[19] When the 1891 Japanese Weights and Measures Act [ja] was promulgated, it defined the shō unit as the capacity of the standard kyo-masu of 64827 cubic bu.
[12][i] 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 [ja] (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.
[6] A lumber koku is conventionally accepted as equivalent to 120 board feet, but in practice may convert to less.
The James Clavell novel Shōgun uses the Koku measure extensively as a plot device by many of the main characters as a method of reward, punishment and enticement.