Japanese houses usually use Tatamis. Nowadays, the number of western-style houses is increasing, but still, tatami is often used as a unit for area sizes.
There are some tatami size variations.
- Shaku-ma(昔間) - 985mm×1970mm
- Kyo-ma(京間) - 955mm×1910mm
- Chukyo-ma(中京間) - 910mm×1820mm
- Edo-ma(江戸間) - 880mm×1760mm
- Danchi-ma(団地間) - 850mm×1700mm
For more info, esswikipedia 畳 (written in Japanese).
1 tsubo is approximately 3.3m2.