1 ri is equal to the product of 36 cho multiplied by 360 (shaku per cho) and then 12960 shaku, because 1 cho is equal to the product of 60 ken (a unit of length) multiplied by 6 (shaku per ken) and then 360 shaku.
1町＝60間×6(尺/間)＝360尺であるので1里＝36町×360(尺/町)＝12960尺となる。