Koku (斛) is a traditional Japanese unit of volume that originated from Chinese measurement systems. It was historically significant, particularly in agricultural and economic contexts within Japan.
Understanding Koku
The koku served as a fundamental unit of measurement, primarily associated with rice. Rice held immense importance in feudal Japan, often functioning as a form of currency or a basis for wealth and status. The volume of a koku was considered sufficient to feed one person for an entire year, underscoring its practical significance in daily life and economic planning.
Koku Equivalences
A single koku represents a substantial volume, reflecting its use for large-scale measurements of goods like rice. The unit has several established equivalences:
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As a unit of volume for liquids or dry goods:
- It is equivalent to 10 to (斗), another traditional Japanese unit of volume.
- Approximately 180 litres (L).
- Roughly 40 imperial gallons (imp gal).
- Around 48 US gallons (US gal).
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As a measure of rice weight:
- When applied to rice, a koku is commonly understood to equate to approximately 150 kilograms (kg) of rice.
- This converts to about 330 pounds (lb) of rice.
To illustrate these equivalences clearly, here is a breakdown:
| Measurement Type | Equivalent Unit | Approximate Value |
|---|---|---|
| Volume | To (斗) | 10 |
| Volume | Litres (L) | 180 |
| Volume | Imperial Gallons | 40 |
| Volume | US Gallons | 48 |
| Rice Weight | Kilograms (kg) | 150 |
| Rice Weight | Pounds (lb) | 330 |
The koku's importance extended beyond mere measurement. It was a crucial factor in the feudal system of Japan, where the wealth and productive capacity of a domain (han) were frequently assessed based on its annual rice output, denominated in koku. This made the koku a direct indicator of economic power, agricultural prosperity, and even the standing of a daimyo (feudal lord).
