The kokudaka (石高) was the tax base calculated regarding koku.

It was an estimate of the annual yield of farmland measured in koku of unpolished rice and the basis of and taxes throughout the Edo Period (1600-1868). The kokudaka system was introduced nationwide by Toyotomi Hideyoshi in the course of his cadastral survey of 1582-1596 and was used until the Land Tax Reform of 1873-1881.

Koku 石

Koku was a measure of volume or capacity, generally used for rice but also for other dry substances and liquids. In the Edo period, a koku of grain was the equivalent of 0.18 cubic metres, 180.39 litres, or 5.12 US bushels. In theory, one koku was enough rice to feed one person for one year. Land productivity, tax assessments, the stipends of the samurai as well as the wealth of daimyō were all calculated in koku.

As a measurement for lumber or ship capacity, one koku equalled ten cubic shaku, or around 0.28 cubic metres (10 cubic feet). Koku was introduced as early as the 7th century CE, but when they were standardised during Hideyoshi's rule, the koku was more than twice its original size.

As the soil and the availability of water affect the yield, paddy fields were classified in four grades with average annual yields (石盛 kokumori) of 1.5, 1.3, 1.2, and 1.1 koku for each tan (about 0.1 hectares of 0.25 acre) of area. Multiplying the kokumori of a paddy field by its number of tan produced its kokudaka (assessed tax base). The productivity of dry fields was calculated similarly. The annual taxes (年貢nengu) were levied on each village within a domain as a percentage of its total kokudaka figure, and the shogunate computed contributions and services from each daimyō by the total kokudaka figure for his domain. The reassessment was infrequent. Therefore farmers and daimyō had every incentive to improve the yield, resulting in a significant increase in agricultural production during the Edo Period. Thus, the kokudama did not reflect the actual amount of food available in a given domain.

Kokudaka replaced kandaka, an annual tax that was agreed upon and calculated in money, used in the Kamakura and Muromachi periods. Simply being a tax base figure, the shogunate could easily vary the amount of taxation due from the farmers by changing the tax rate. Kokudaka was calculated in kind which protected the farmers - though not the daimyō - from price fluctuations in an increasingly money-based economy.

Major daimyō houses around 1664 ranked by kokudama

-Daimyō houseDomainTypeCastle townKokudaka
1Maeda (前田)*Kanazawa (Kaga)TKanazawa1,022,700
2Shimazu (島津)SatsumaTKagoshima770,000
3Date (伊達)SendaiTSendai625,600
4Tokugawa (徳川)Owari (Nagoya)SNagoya619,500
5Tokugawa (徳川)Kii (Wakayama)SWakayama555,000
6Hosokawa (細川)KumamotoTKumamoto540,000
7Matsudaira (松平)Fukui (Echizen)SFukui447,000
8Kuroda (黒田)FukuokaTFukuoka430,000
9Asano (淺野)Hiroshima (Aki)THiroshima426,000
10Mōri (毛利)*Chōshū (Hagi)THagi369,000
11Tōdō (藤堂)*Anotsu (Tsu)TTsu323,900
12Ikeda (池田)TottoriTTottori320,000
13Ikeda (池田)OkayamaTOkayama315,000
14Ii (井伊)HikoneFHikone300,000
15Tokugawa (徳川)MitoSMito280,000
16Hachisuka (蜂須賀)TokushimaTTokushima257,900
17Yamanouchi (山ノ内)Tosa (Kōchi)TKōchi200,000

Alternative domain names in parentheses.
* House name sometimes also used as domain name.
S: shinpan; F: fudai, T: tozama

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