Area Unit Converter

Conversion basis

• 1 tsubo = 3.305785 ㎡ ≈ 2 tatami
• 1 tatami (jō) = 1.62 ㎡ (real-estate advertising standard)
• 1 ㎡ = 0.3025 tsubo ≈ 0.62 tatami

Units for measuring home size

In Japan, floor area is expressed in tsubo (坪), square metres (㎡) and tatami (畳 / 帖). Tsubo is common for land and buildings, square metres for registration and design, and tatami as an intuitive sense of room size. One tsubo is about 3.31 ㎡ — roughly two tatami mats. Switching between units makes it far easier to compare layouts and prices.

Tatami size varies by region

“畳” and “帖” are the same unit (both read jō); 帖 is used mainly for non-tatami (flooring) rooms. This tool computes a tatami at the 1.62 ㎡ advertising standard. Actual tatami differ by region, as below.

Type	Approx. per tatami
Kyōma / Honma	≈ 1.82 ㎡
Chūkyōma	≈ 1.66 ㎡
Edoma (Kantō)	≈ 1.55 ㎡
Danchima	≈ 1.45 ㎡
Advertising standard	1.62 ㎡

Living-area standards (Housing Master Plan)

Japan's Housing Master Plan (MLIT) sets a “minimum living-area standard” and a more generous “induced living-area standard” (urban and general types) according to household size.

Household	Minimum	Induced (urban)	Induced (general)
Single	25㎡	40㎡	55㎡
2 people	30㎡	55㎡	75㎡
3 people	40㎡	75㎡	100㎡
4 people	50㎡	95㎡	125㎡

For a three-person household, for example, the minimum is 40 ㎡ (about 12 tsubo) and the general induced target is 100 ㎡ (about 30 tsubo). Use the converter above to see these in tsubo or tatami.

Wall-centre vs. internal area (壁芯・内法)

The same dwelling can show different areas depending on how it is measured. “Wall-centre” area (壁芯) is measured to the centre of the walls — used for building permits and advertising — and reads slightly larger. “Internal” area (内法) is measured to the inner face of the walls — used on the property register, for condominium floor area and for the mortgage tax deduction — and is a few percent smaller. That is why an advertised area and a registered area can differ.

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