Japan Data

Traditional Japanese Units of Measurement for Length and Weight

Society History

Japan’s traditional units of measurement for length and weight include the monme (3.75 grams), which has become an internationally recognized standard for weighing pearls.

The metric system was introduced to Japan in the late nineteenth century, but traditional units for length and weight remained in use. The passing of legislation in the 1950s, however, made the metric system official. Traditional measurements are now much less prominent, although they still linger in crafts and other cultural domains.


The best-known traditional units of length are the sun (3.03 centimeters) and shaku (30.3 centimeters). The word sunpō, meaning size, includes sun. There is also a fairy tale character called Issunbōshi, or “One sun boy,” similar to the English folk character Tom Thumb.

The shakuhachi is a bamboo flute, which is said to take its name from its traditional length of one shaku eight sun (hachi means eight). Note, however, that traditional units could vary considerably in length before the introduction of standardization.

1/10 sun 1 bu (分) 3.03 mm
1/10 shaku 1 sun (寸) 3.03 cm
1 shaku (尺) 30.3 cm
6 shaku 1 ken (間) 1.818 m
60 ken 1 chō (町) 109.9 m
36 chō 1 ri (里) 3.927 km


The monme, equivalent to 3.75 grams, is the most commonly used traditional Japanese weight. For example, a ¥5 coin weighs exactly one monme. Under a different spelling, the momme is an internationally recognized weight used by pearl dealers.

1/1000 kan 1 monme (匁) 3.75 g
1 kan (貫) 3.75 kg
160 monme 1 kin (斤) 600 g
100 kin 1 hyō (俵) 60 kg

(Translated from Japanese. Banner image: A tradesman measures confectionery using a scale and weights. From Shokunin zukushi utaawase [Poetry Contest by Various Artisans]. Courtesy National Diet Library.)

Edo period measurement