A 1R/1K apartment in Japan is typically 13–25 m² (4–8 坪 / 평).
From a Japanese listing
Tatami size varies by region — the same “6畳” can differ by 15%+. Listings legally must also show ㎡.
1R/1K
🏠 A compact studio (1R/1K) — fine for one person.
㎡ is the legal size. 畳/坪 are traditional — always cross-check the ㎡ figure.