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

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