Tatami (畳 たたみ)
Tatami, floor mats for Japanese‐style rooms, are filled with woven rice straw and covered with finely‐woven rush. The normal size of one tatami is 180 centimeters long and 90 centimeters wide (approximately 6 feet by 3 feet); the size of Japanese‐style rooms is measured by the number of tatami. It is said that tatami are a suitable material for the humid weather of Japan.
When you look at the room layout when you rent an apartment in Japan for example, the size of the room is represented by Tatami such as 6 Tatami mats or 4.5 Tatami mats. A 6 mat room is a general size and a 4.5 mat room is small for many people. The general perception of Japanese is that 8 tatami mats are large.