Converting Tsubo and Square Meters: How Many m² Is 1 Tsubo, Calculating Tsubo and Price per Tsubo

How many m² is 1 tsubo? Why it's 3.3058 m²

The tsubo is an area unit from Japan's traditional shakkan system, and 1 tsubo is a square 1 ken (6 shaku) on each side. Japan's Measurement Act defines 1 shaku as 10/33 m, so 1 tsubo is (6 × 10/33)² = 400/121 m², or about 3.3058 m² as a decimal. It doesn't divide evenly, so different sources round it differently (3.31 m², 3.306 m²), but the underlying value is the same.

• Tsubo → m²: tsubo × 3.3058. 30 tsubo is 30 × 3.3058 = 99.17 m².
• m² → tsubo: m² × 0.3025. 70 m² is 70 × 0.3025 = 21.18 tsubo.
• Mental math: for tsubo, "multiply by 3 and add 10%"; for m², "divide by 3 and take off a little". Being able to tell that 100 m² is a bit under 33 tsubo is good enough.

It also helps to know how tsubo relate to tatami mats. Two 6 × 3 shaku mats (chūkyōma size) side by side make exactly 1 tsubo. Mat size varies by region and building type, though, so be careful when working back from the number of mats on a floor plan to the actual area. The differences between standards are summarized in How many m² is a 6-mat room?.

Tsubo → m² and m² → tsubo charts

These are numbers that come up often in listings. Mat counts use the Japanese property-advertising standard (1 mat = 1.62 m²).

Remember one typical pair, such as a 70 m² family condominium being about 21 tsubo or a 30-tsubo house being about 99 m², and you'll get a sense of scale the moment you see a flyer.

Site area, building footprint and total floor area are different numbers

A "30-tsubo house" means different things depending on whether it refers to the land or the building. Start by telling these four areas apart.

• Site area (land area): the land seen from directly above. On sloping land it comes out smaller than the area you can actually walk on.
• Building area (footprint, kentsubo): the building seen from directly above. For a two-storey house it's usually the ground floor area.
• Total floor area: the sum of the floor areas of every storey. A "30-tsubo house" usually means this number.
• Construction floor area: the builder's figure, including balconies, open-ceiling spaces and the entrance porch. It's larger than the total floor area.

For condominiums there's one more thing to watch: wall-center area (hekishin) versus inner area (uchinori). Sales brochures use the wall-center area, measured to the center line of the walls, while the land register uses the inner area, measured inside the walls, so the registered figure for the same unit is a few m² smaller. A unit advertised at 70 m² may be registered at 67-something m², so whenever a decision depends on an area threshold, always check which figure is meant.

Calculating price per tsubo, and pitfalls when comparing

Price per tsubo is the building price divided by the total floor area in tsubo. It's a way of putting houses that are hard to compare on total price alone on an equal footing.

1. 1

   Convert the total floor area to tsubo

   A total floor area of 99.17 m² is 99.17 × 0.3025 = 30 tsubo.

2. 2

   Divide the building price by the tsubo

   A base price of ¥24 million ÷ 30 tsubo = ¥800,000. That's the price per tsubo.

3. 3

   Check what the price includes

   Whether ancillary work is included (outdoor plumbing and drainage, ground improvement, lighting, curtains, etc.) moves the price per tsubo a lot. Quotes that leave it out look cheaper.

4. 4

   Check whether the divisor is total or construction floor area

   Dividing by the construction floor area makes the divisor larger, so the same house shows a lower price per tsubo. When comparing builders, use the same divisor.

Converting between price per m² and price per tsubo uses the same factors. ¥240,000 per m² is 24 × 3.3058 = about ¥793,000 per tsubo; conversely, ¥800,000 per tsubo is 80 × 0.3025 = ¥242,000 per m². When comparing land prices, also line up whether prices include tax and brokerage fees before putting them side by side. Converting between tax-inclusive and tax-exclusive prices is covered in Japan's total price display rule, and working out prices after a discount in How to calculate discounts. To work back to how large a total budget is realistic, see How to calculate how much you can borrow.

Convert everything at once with the tool

Working out tsubo, m² and tatami one by one on a calculator leads to numbers that don't match because of rounding. The Unit Converter converts into every unit in the same category at once, so it's also handy for notes when viewing properties.

1. 1

   Choose "Area"

   It starts at tsubo → m². Switching to m² → tsubo is one tap on the Swap button.

2. 2

   Enter the number

   Type in the number from the flyer as is. m², tsubo, tatami, tan and acres are all shown at the same time.

3. 3

   Choose the tatami standard

   If you use mat counts, switch the standard between property advertising (1.62 m²), kyōma, chūkyōma, edoma and danchima. The standard you choose can shift the mat count by one or more.

4. 4

   Copy the quick-reference table

   You can copy the table listing 1, 2, 3, 5, 10 and so on as is. When making a list of candidate properties, pasting tsubo and m² side by side speeds up comparison.

Traditional shakkan units survive in more than area. Length units such as shaku, sun and ken are covered in Converting inches and cm, and the volume units gō and shō in How many ml is 1 gō?.

FAQ

How many square meters is 1 tsubo?

1 tsubo is 400/121 m², about 3.3058 m² as a decimal. It's a square 1 ken (6 shaku) on each side, calculated from the Measurement Act's definition of 1 shaku = 10/33 m. In practice it's often rounded to 3.31 m²; multiply tsubo by 3.3058 to get m². To go from m² back to tsubo, multiply by 0.3025. That factor is exact, so on a calculator m² × 0.3025 leaves no rounding worries.

What's the formula for converting m² to tsubo?

Tsubo = m² × 0.3025. 80 m² is 80 × 0.3025 = 24.2 tsubo, and 100 m² is 30.25 tsubo. Dividing by 3.3058 gives the same answer, but multiplying is less prone to typing mistakes. For mental math, think "divide by 3 and take off just under 10%", so 100 m² is a little under 33 tsubo. When you need an exact figure, check with the Unit Converter.

How many tatami mats make 1 tsubo?

With 6 × 3 shaku chūkyōma mats, exactly 2 mats make 1 tsubo. But mat sizes include kyōma (1.824 m²), chūkyōma (1.656 m²), edoma (1.549 m²) and danchima (1.445 m²), and Japanese property adverts use a standard of 1 mat = 1.62 m² or more. On the advertising standard, 1 tsubo is about 2.04 mats, and with danchima about 2.29 mats, so "1 tsubo = 2 mats" is only a rule of thumb.

Why does an advertised 70 m² differ from the area in the land register?

Condominium brochures use the wall-center area, measured to the center line of the walls, while the land register uses the inner area, measured inside the walls. The inner area is smaller by the thickness of the walls, and a 2–3 m² difference for a unit in the 70 m² range isn't unusual. Neither is wrong; they're measured differently. For procedures where the area threshold changes the outcome, first check which figure is required.

Can price per tsubo be converted to price per m²?

Yes. Price per tsubo × 0.3025 = price per m², and price per m² × 3.3058 = price per tsubo. ¥800,000 per tsubo is about ¥242,000 per m². But price per tsubo depends on the divisor: whether you divide by total or construction floor area, and whether ancillary work is included, can move it by around 10%, so align the divisor and the included work before comparing.