Tatami, tsubo and square metre converter
Result
6 jō (Edoma mats) = 9.29 square metres (m²)
| square metres (m²) | 9.29 |
|---|---|
| tsubo | 2.81 |
| jō (Kyōma mats) | 5.09 |
| jō (Rokuichima mats) | 5.43 |
| jō (Chūkyōma mats) | 5.61 |
| jō (Danchima mats) | 6.43 |
| Max. jō a property ad may claim | 5.74 |
Figures are rounded to 2 decimal places.
Tatami sizes differ by region and building. "1.62 m²" is the smallest floor area (measured to the wall centres) that a Japanese property ad may call one jō; it is not the size of a mat.
Tatami count to square metres
| Mats (jō) | Kyōma | Rokuichima | Chūkyōma | Edoma | Danchima | Ad min. |
|---|---|---|---|---|---|---|
| 1 | 1.82 | 1.71 | 1.66 | 1.55 | 1.45 | 1.62 |
| 2 | 3.65 | 3.42 | 3.31 | 3.10 | 2.89 | 3.24 |
| 3 | 5.47 | 5.13 | 4.97 | 4.65 | 4.34 | 4.86 |
| 4.5 | 8.21 | 7.70 | 7.45 | 6.97 | 6.50 | 7.29 |
| 6 | 10.94 | 10.27 | 9.94 | 9.29 | 8.67 | 9.72 |
| 8 | 14.59 | 13.69 | 13.25 | 12.39 | 11.56 | 12.96 |
| 10 | 18.24 | 17.11 | 16.56 | 15.49 | 14.45 | 16.20 |
| 12 | 21.89 | 20.54 | 19.87 | 18.59 | 17.34 | 19.44 |
Area = number of mats × mat length × mat width (inside the walls). Measured to the wall centres, a room is larger. “Ad min.” is the smallest wall-centre area a property ad needs, at 1.62 m² per jō.
Tsubo to square metres
| tsubo | square metres (m²) | jō (Edoma mats) |
|---|---|---|
| 1 | 3.31 | 2.13 |
| 5 | 16.53 | 10.67 |
| 10 | 33.06 | 21.34 |
| 20 | 66.12 | 42.69 |
| 30 | 99.17 | 64.03 |
| 40 | 132.23 | 85.38 |
| 50 | 165.29 | 106.72 |
| 100 | 330.58 | 213.44 |
How it is calculated
One tsubo is 400/121 m² (about 3.31 m²). Article 4 of the Act for Enforcement of the Measurement Act (計量法施行法, in force from 1952; the English name is our translation) defined it that way. The same article sets one shaku at 10/33 m and, under Article 5, one ken is 6 shaku, so one tsubo is the area of a square one ken on each side.
No law sets the size of a tatami mat; it varies with regional custom. This page uses the sizes in a table from the Ministry of Land, Infrastructure, Transport and Tourism (in Japanese): Kyōma 1910 × 955 mm, Rokuichima 1850 × 925 mm, Chūkyōma 1820 × 910 mm, Edoma 1760 × 880 mm and Danchima 1700 × 850 mm. Area = number of mats × mat length × mat width (inside the walls, not to the wall centres).
In a Japanese property ad, “6 jō” means each jō stands for at least 1.62 m² of floor area measured to the wall centres (Article 9, item 16 of the Enforcement Rules of the Fair Competition Code for Real Estate Advertising, in Japanese; this is an industry code, and the English name is our translation).
The figures and rules on this page were checked item by item by an AI (Claude) against the sources above on 2026-10-30. No person has reviewed them.
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FAQ
How many square metres is one tatami mat?
It depends on the mat size. Using the sizes in the Ministry of Land, Infrastructure, Transport and Tourism table, a Kyōma mat is about 1.82 m², Rokuichima about 1.71 m², Chūkyōma about 1.66 m², Edoma about 1.55 m² and Danchima about 1.45 m². In property ads, one jō means at least 1.62 m² measured to the wall centres.
How big is one tsubo?
One tsubo is 400/121 m², about 3.31 m². It is a square one ken (6 shaku) on each side, which is the area of two Chūkyōma mats if each mat is taken as exactly 6 × 3 shaku. That is about 2.13 Edoma mats or 1.81 Kyōma mats.
How many square metres is a “6-jō” room in a Japanese listing?
In a property ad, each jō must stand for at least 1.62 m² of floor area measured to the wall centres, so a 6-jō room is at least 9.72 m². The number of mats that would actually fit can differ, so check the area given in square metres.