Tatami

Tatami has 4 types:

京間

きょうま

Used in 関西・中国・四国・九州.
1.91mx0.955m, 6 = 10.94㎡

中京間 (or 三六間)

ちゆうきようま

Used in 愛知・岐阜・三重

1.91mx0.955m, 6 = 9.93㎡

Horizontally 3m
Vertically 6m

江戸間 (or 五八間)

えどま

関東

1.76mx0.878m, 6 = 9.27㎡

Vertically 5.8m

団地間 (or 五六間)

だんちま

1.7mx0.85m, 6 = 8.67㎡

Vertically 5.6m

When people in Kansai moved to Kanto, they felt smaller, this is why :-)