Koku was the Japanese term for the rice-measured stipend that often represented a samurai retainer’s income. One koku was conventionally defined as the amount of rice needed to feed one person for a year, although actual standards and measurements varied across periods.
Rice taxation and assessment became central to domain administration, especially under the Tokugawa shogunate. Domains and retainers were often described by kokudaka, the estimated annual agricultural production measured in koku. A daimyo’s rank and political importance were closely connected to the assessed yield of his domain.
Koku was an accounting unit rather than a literal bag of rice delivered every year. Samurai stipends could be paid partly or entirely in money, and rice prices affected real purchasing power. The term should also be distinguished from ryō, a monetary unit used in early modern Japan. Despite these complications, koku remains one of the clearest measures of the economic foundation of samurai rule.