🟫 Tatami Area Calculator (Jo to m2)

The Tatami Area Calculator converts room areas measured in jo (畳 or 帖, tatami mats) into metric and imperial units. In Japan, room sizes are traditionally expressed by the number of tatami mats they contain - a custom dating back over 400 years.

Tatami mat dimensions vary by region and era. The three standard sizes are:

The character 畳 is used for Japanese-style rooms (washitsu), while 帖 is used for Western-style rooms and in real estate listings to avoid ambiguity. Both are read as "jo" and represent the same unit concept.

The calculator multiplies the number of tatami mats by the area of a single mat, based on the selected tatami type:

Edoma: 1 jo = 1.62 m2 (17.44 ft2). A 6-jo room = 9.72 m2.

Kyoma: 1 jo = 1.82 m2 (19.59 ft2). A 6-jo room = 10.92 m2.

Danchima: 1 jo = 1.45 m2 (15.61 ft2). A 6-jo room = 8.70 m2.

For tsubo conversion: 1 tsubo = 3.306 m2. At this calculator's Edoma size (1.62 m2 per mat), a 6-jo room is about 2.94 tsubo; the neat 2 mats per tsubo / 3 tsubo per 6-jo ratio only holds under the older 1.653 m2-per-mat convention.

For broader area conversions, try our tsubo converter or the general area converter. To measure room dimensions, the Pythagorean calculator can help with diagonal measurements.

1. Enter the number of tatami mats (jo) - e.g. 6 for a standard room.
2. Select the tatami type: Edoma, Kyoma, or Danchima.
3. Click Calculate to see the area in m2, ft2, tsubo, and bu.
4. Review the comparison table for all three tatami sizes.

What is the difference between 畳 and 帖?

Both are read as "jo" and represent the same floor area concept. Since 2017, Japanese real estate guidelines use 畳 for Japanese-style rooms (washitsu) and 帖 for Western-style rooms (youshitsu). This distinction prevents buyers from assuming a room has actual tatami flooring.

How big is a 6-tatami room in square meters?

It depends on the tatami type. Edoma (Tokyo): 9.72 m2. Kyoma (Kansai): 10.92 m2. Danchima (apartments): 8.70 m2. Edoma 6-jo is the most common standard cited in real estate.

Why do Japanese rooms use tatami count instead of square meters?

Tatami mats were the standard flooring for centuries, so room sizes evolved around mat dimensions. Even modern apartments are described as "6-jo" because Japanese people intuitively understand how big that feels, more so than 9.72 m2.

What is yojo-han (4.5 jo)?

Yojo-han (四畳半) means 4.5 tatami mats. It uses 4 full mats plus one half mat (han-jo). This layout is common in older apartments, tea rooms (chashitsu), and budget accommodations. The half-mat fills the center gap in a non-grid arrangement.

How many tatami mats are in one tsubo?

One tsubo (坪) equals 3.306 m2. A 6-jo Edoma room at this calculator''s 1.62 m2 per mat comes to about 2.94 tsubo; the 3-tsubo figure only holds under the older 1.653 m2-per-mat convention.

Real estate listings use 帖 not 畳 for Western-style rooms. The 2017 JUTAKU SEIKAKU handbook standardized this: 畳 = washitsu (tatami room), 帖 = yousetsu (Western room). Both count floor area the same way.

Tatami count affects property value. Standard apartment layouts: 1K = 4.5 jo, 1DK = 6 jo, 1LDK = 8 jo. A 6-jo room is considered the minimum comfortable size for one person.

The 4.5-jo room (yojo-han) is a uniquely Japanese layout with 4 full mats plus a half mat. It is common in older apartments and tea ceremony rooms.

For floor area ratio (yosekiritsu) calculations in real estate, always confirm which tatami standard the listing uses. Edoma is most common in Tokyo; Kyoma in Kansai. A 6-jo Edoma room (9.72 m2) is about 12% smaller than a 6-jo Kyoma room (10.92 m2).