Koku, traditional Japanese unit of volume

During the medieval period, one koku was a volume unit defined as the rice quantity necessary to feed a person for one year. Converted, one koku was about 180 liters, meaning around 150 kilograms of rice, which was two and a half rice straw bales such as the ones in this photo taken inside the museum of Sankyo Warehouses in Sakata, Yamagata.

For each feudal domain, potential revenue was calculated in a number of koku, ranging from 10,000 (for the smallest) to a million koku (which was the value of the Kaga domain). The monetary system was also based on koku, thus the 1 ryu coin was the equivalent of one koku.