Tatami Sizes by Region: Kyoma, Edoma, and More

One of the more surprising discoveries for people studying Japanese architecture, apartment hunting in Japan, or renovating a traditional Japanese room is that tatami mats — the tightly woven rush-grass floor coverings that define the aesthetic of the traditional Japanese interior — are not a single standardised size. A room listed as "six tatami" (六畳, rokujo) in Kyoto is meaningfully larger than a room with the same description in Tokyo, and both differ from a room in Nagoya or a post-war public housing complex. This regional variation has deep historical roots in the construction philosophy of feudal-era Japan, and it continues to affect how apartments are advertised, how room areas are estimated, and how the physical experience of space varies across the country.

Tsubo Converter

The Four Main Standards

Japan formally recognises four principal tatami size standards, each named after the region or era in which it predominates:

Standard	Kanji	Main Region	Dimensions	Area per Mat
Kyōma	京間	Kyoto / Kansai	191 cm × 95.5 cm	~1.824 m²
Chūkyōma	中京間	Nagoya / Tōkai	182 cm × 91 cm	~1.656 m²
Edoma (Kantōma)	江戸間 / 関東間	Tokyo / Kantō	176 cm × 88 cm	~1.549 m²
Danchima	団地間	Public housing nationwide	170 cm × 85 cm	~1.445 m²

Tatami To Sqm

The Kyōma mat, at 191 × 95.5 cm, is the largest common standard. The Danchima mat, at 170 × 85 cm, is the smallest. The practical consequence of this size spread is significant: a six-tatami room (rokujo) in Kyoto (6 × 1.824 m² = 10.94 m²) is larger by more than 2.25 m² than the same room in a Tokyo danchi (6 × 1.445 m² = 8.67 m²). That difference is roughly the floor area of a large bathtub and matters considerably in small Japanese apartments where every square centimetre is negotiated.

Why the Sizes Diverged Historically

The divergence reflects two fundamentally different philosophies of construction standardisation that developed in different parts of Japan during the feudal period:

The Kyōma approach — room-first design (柱割り, hashira-wari): Rooms were dimensioned first, fixed as multiples of the ken (間, approximately 181.8 cm) grid derived from structural post spacing. Tatami were then measured and cut precisely to fill the resulting space, including the slight gaps around pillar bases. This room-centred approach produced the larger Kyōma mat because the room dimensions were generous imperial court standards.

The Edoma approach — mat-first design (畳割り, tatami-wari): The tatami mat itself was the fixed unit, and rooms were designed to accommodate a specified number of mats, with structural posts positioned accordingly. This mat-centred approach produced a somewhat smaller mat because builders optimised for efficient material use in Edo's rapidly expanding commoner neighbourhoods. The Edoma convention thus reflected the pragmatic construction economics of a large mercantile city.

The Chūkyōma standard emerged in central Japan (the Nagoya-Gifu-Mie region) as an intermediate between the Kyoto and Edo conventions, reflecting the cultural and commercial position of this corridor as a bridge between the imperial west and the shogunal east.

The Danchima standard was a deliberate post-war innovation. As Japan built massive danchi (団地, public housing estates) to house the millions of people migrating from rural areas to industrial cities, architects optimised for construction efficiency. Slightly smaller mats meant more rooms per building and lower material costs — a practical engineering decision that created a permanent fourth standard.

Converting Tatami to Square Metres by Region

When Japanese apartment listings give room sizes in tatami (e.g., 和室6畳 — Japanese-style room, 6 mats), you need to know which regional standard applies to convert to square metres. Unfortunately, listings frequently omit this critical detail. As a practical guide based on property age and location:

• Old Kyoto, Kansai machiya (町家, traditional townhouses): Almost certainly Kyōma.
• Modern Kansai construction (Osaka, Kobe, Nara): Typically Kyōma or Chūkyōma.
• Central Japan (Nagoya, Gifu, Mie, Shizuoka): Typically Chūkyōma.
• Tokyo and Kantō region: Typically Edoma (Kantōma).
• Post-war public housing complexes (danchi) nationwide: Danchima.
• Modern private condominium buildings anywhere: Often use a nominal tatami size that varies by developer; the specific mat size may be entirely notional, and the listed square metres are a more reliable size indicator.

Tsubo To Sqm

The Historical Two-Tatami-per-Tsubo Relationship

The tsubo (坪) was traditionally defined as the area of two standard tatami mats laid side by side — this is the historical connection between the two area units. However, since regional standards have produced tatami of varying sizes, the actual relationship between tatami and tsubo depends on which standard is in use:

Standard	Area per mat	Mats per tsubo (exact)
Kyōma	1.824 m²	~1.81 mats
Chūkyōma	1.656 m²	~1.99 mats
Edoma	1.549 m²	~2.13 mats
Danchima	1.445 m²	~2.29 mats

Only the Chūkyōma mat comes close to the historical two-mats-per-tsubo definition. The Kyōma mat is actually larger than the historical baseline; the Edoma and Danchima mats are meaningfully smaller.

Practical Advice for Apartment Hunters

When comparing properties that use tatami-count sizing, always request the senyū menseki (専有面積, exclusive floor area in square metres) from the landlord or agent, and use tatami counts primarily as a guide to the room's layout and character rather than its absolute floor area. Two apartments both described as "six-tatami" in the same city may differ by only a few percent; two apartments in different cities may differ by nearly 25%. For renovation projects or furniture ordering, always measure the actual room rather than relying on the tatami specification. Use Tsubo Converter to convert between area units with full regional-standard precision.

Tatami in Modern Interior Design

Despite the prevalence of Western-style flooring in contemporary Japanese apartments, tatami retains a strong presence in Japanese interior design culture. Surveys consistently show that a significant proportion of Japanese people — particularly those in their 40s and older — prefer at least one washitsu (和室, Japanese-style tatami room) in their home. The tatami room serves multiple functions: it can be used as a bedroom (with futon laid directly on the mats), a tea ceremony space, a meditation or yoga room, a guest room, or simply a calming retreat with a distinctly Japanese aesthetic.

Tatami's appeal is partly sensory: the smell of fresh rush (igusa, 藺草) — the plant used to weave the mat surface — is strongly associated with comfort and home in Japanese culture, in a way that has no direct equivalent in Western interior experience. New tatami mats have a fresh, grassy scent that fades over months of use, and replacing tatami is part of the maintenance cycle of traditional Japanese homes.

The tatami industry has responded to the declining floor space of modern apartments by developing compact formats: hankei (半畳, half-size mats), tile tatami (uketami, 置き畳 — individual tatami tiles that can be placed on existing wooden floors without structural modification), and synthetic tatami using polypropylene igusa substitute that maintains the traditional aesthetic without the maintenance requirements of natural rush. These innovations are expanding tatami's presence in younger households and smaller apartments where a dedicated washitsu would be impractical.