A 1DK apartment in Japan is typically 25–30 m² (8–9 坪 / 평).
From a Japanese listing
Tatami size varies by region — the same “6畳” can differ by 15%+. Listings legally must also show ㎡.
1DK
🏠 A 1LDK — comfortable for one, snug for a couple.
㎡ is the legal size. 畳/坪 are traditional — always cross-check the ㎡ figure.