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The measures of old Japan, from the sun to the ri. Part of the Ancient Measures collection.
Every unit converts through meters: shaku = 10/33 m (0.30303 m) exactly, sun = shaku/10, ken = 6 shaku, cho = 360 shaku, ri = 36 cho. Worked example: a marathon’s 42.195 km = 42,195 / 3927 ≈ 10.74 ri — the Tokyo-Hakone ekiden’s ~217 km is about 55 ri. The shaku came from Tang China’s chi; Japan froze it in 1891 while China’s chi kept drifting — cousins, no longer twins.
Exactly 10/33 m = 30.303 cm, fixed by law in 1891. It descends from Tang China’s chi — the two parted ways a millennium ago.
6 shaku, 1.818 m — the module of Japanese architecture. Rooms are counted in tatami mats, and mats are sized in fractions of a ken.
In construction and traditional crafts, yes — carpenters still think in shaku and sun, and land is still described in tsubo (square ken).
Japanese Weight Japanese Volume Chinese Length Roman Length Russian Length