A koku (石) is a quantity of rice, historically defined as enough rice to feed one person for one year, then as 180.39 litres, or about 5 bushels (40 Imperial or 48 US gallons).
A koku (石) is a quantity of rice, historically defined as enough rice to feed one person for one year. In 1891 it was defined such that one koku equalled exactly 240100/1331 litres, this is approximately 180.39 litres, or about 5 bushels (40 Imperial or 48 US gallons).