4.5 jô (= size of a tatami), which is the unit of surface most commonly used for apartments in Japan. 1 jô = a little less than 2 m^2. https://en.wikipedia.org

4.5 jô (= size of a tatami), which is the unit of surface most commonly used for apartments in Japan. 1 jô = a little less than 2 m^2. https://en.wikipedia.org/wiki/Tatami https://en.wikipedia.org/wiki/Tatami (section "Size")