Tatami are made in standard sizes, with the length exactly twice the width,
an aspect ratio of 2:1.
In Japan the size of a room is often measured by number of Tatami mats
(1 Tatami = 1 JO = 1,653 ㎡).
Alternatively, in terms of traditional Japanese area units, room area is
measured in terms of TSUBO. (1TSUBO = 2 Tatami – 3,306 ㎡)