The Japanese unit system is just as complicated and
chaotic as the English system. The tables below show the
correspondence with the One True System.
Warning: not only some terms have meanings in
several unit systems (length, weight, etc), but sometimes two
different written words are pronounced the same way (shaku, bu,
chou). In that case, I capitalized one of the words to avoid any
confusion: shaku and Shaku will refer to completely different
Japanese words.
Length Units:
1 mou = 0.001 sun = 0.03 mm
1 rin = 0.01 sun = 0.3 mm
1 sun = 3.03 cm
1 shaku = 10 sun = 30.3 cm
1 ken = 6 shaku = 1.818 m
1 hiro = 6 shaku = 1.818 m (water depth)
1 jou = 10 shaku = 3.03 m
1 hiki = 21 m (length of cloth)
Former length units:
1 Bu = 0.1 sun = 3.03 mm
1 Chou = 60 ken = 109.8 m
1 ri = 36 chou = 3927 m
Area Units:
1 Shaku = 330.5 cm2
1 bu = 36 Shaku2 = 3.3 m2
1 tsubo = 1 bu = 3.3 m2
1 se = 30 bu = 0.99 are
1 tan = 300 bu = 991 m2
1 chou = 10 tan = 0.99 hectare
A special area unit is the tatami, or jou, which is a rectangle of 3
shaku by 6 shaku.
Former area units:
1 gou = 10 Shaku = 0.33 m2
Volume Units:
1 Shaku = 0.018 l
1 gou = 0.18 l
1 shou = 10 gou = 1.8 l
1 to = 10 shou = 18 l
1 sai = 1 Shaku3 = 3.78 l (lumber, freight)
1 tsubo = 216 Shaku3 = 6000 l (earth)
Former volume units:
1 koku = 1 to = 180 l (rice stipends)
1 koku = 10 shaku3 = 278 l (lumber)
Weight units:
1 monme = 3.75 g
1 me = 1 monme = 3.75 g
1 kin = 160 monme = 601 g
1 kan = 1000 monme = 3.75 kg
Former weight units:
1 mou = 0.001 monme = 3.75 mg
1 rin = 0.01 monme = 37.5 mg
1 fun = 0.1 monme = 375 mg
1 ryou = 10 monme = 37.5 g