Converting Lengths Used in Edo-Period Carpentry to Meters

The calculation was based on 1 shaku = 10/33 meters. One shaku is the length of the forearm, and one ken (6 shaku) is approximately the height of a person. Furthermore, since a tatami mat measures 6 shaku by 3 shaku, the units of length used in the Edo period were closely tied to daily life and were, in some ways, quite practical. It is unacceptable to say “even a 3-centimeter insect has a 1.5-centimeter soul” instead of “even a 1-sun insect has a 5-bun soul.”
To distinguish it from the “kujira-jaku” (whale ruler) used in kimono tailoring, it is sometimes referred to as the “kane-jaku” (carpenter’s square).