A 1LDK apartment in Japan is typically 30–50 m² (9–15 坪 / 평).
From a Japanese listing
Tatami size varies by region — the same “6畳” can differ by 15%+. Listings legally must also show ㎡.
1LDK
🏠 A 2LDK — couple or small family.
㎡ is the legal size. 畳/坪 are traditional — always cross-check the ㎡ figure.