📐 Tsubo⇔㎡ (Sqm) Converter

Tsubo is a traditional Japanese area unit based on the shakkanhō measurement system. One tsubo equals approximately 3.30579 square meters (㎡), roughly the size of two tatami mats (Kyoma standard). In modern Japan, it is widely used especially in the real estate industry and serves as an important unit for expressing the area of land and buildings. The origin of tsubo dates back to the Edo period, established based on the surveying techniques and lifestyle of that era. One tsubo is defined as one ken (ikken) square, approximately 1.818 meters on each side. This unit is closely related to Japanese architectural culture and residential design, remaining an intuitively understandable area expression for many Japanese people today. While ㎡ notation is legally required in real estate advertisements and property information, tsubo numbers are commonly listed alongside to aid customer understanding.

Square meters (平米, heibei in Japanese) are area units based on the International System of Units (SI). One square meter is the area of a one-meter square, meaning 1m×1m=1㎡. Following the 1966 revision of the Measurement Act, ㎡ notation became mandatory in official documents and legal papers in Japan. Real estate registries, building confirmation applications, and fixed asset tax assessment certificates must all use ㎡ notation. However, in actual real estate transactions, tsubo notation is commonly used alongside ㎡ notation to aid customer understanding. This dual notation enables information provision that accommodates both traditional sensibilities and international standards. Globally, ㎡ is used as the standard area unit, making ㎡ notation essential in international real estate transactions and construction projects.

Tatami is a unit indicating the area of one traditional Japanese floor mat. However, tatami sizes vary by region and era, requiring caution in area conversion. Major tatami sizes include: Kyoma (Honma/Kansaima) at 1.82m×0.91m (approximately 1.65㎡), Chukyoma (Sanrokuma) at 1.82m×0.91m, Edoma (Kantōma/Gohachima) at 1.76m×0.88m (approximately 1.55㎡), and Danchima (public housing size) at 1.70m×0.85m (approximately 1.45㎡). Between the largest Kyoma and smallest Danchima, there is approximately 0.2㎡ difference per tatami. When a real estate advertisement states "6-tatami room," based on Kyoma standard it would be approximately 9.9㎡, while Danchima standard would be approximately 8.7㎡, resulting in approximately 1.2㎡ (approximately 0.36 tsubo) difference. Therefore, checking ㎡ notation is crucial for knowing accurate area.

Converting between tsubo and square meters uses the precise conversion factor of 1 tsubo = 3.30579㎡. In practice, simplified calculations using 1 tsubo ≈ 3.3㎡ are also common. The conversion formulas are: converting ㎡ to tsubo uses "㎡ ÷ 3.30579 = tsubo," while converting tsubo to ㎡ uses "tsubo × 3.30579 = ㎡." Practical conversion examples include: 10 tsubo equals approximately 33.06㎡ (about 20 tatami), 20 tsubo equals approximately 66.12㎡ (about 40 tatami), 30 tsubo equals approximately 99.17㎡ (about 60 tatami, typical family apartment), 50 tsubo equals approximately 165.29㎡ (about 100 tatami, spacious detached house), and 100 tsubo equals approximately 330.58㎡ (about 200 tatami, large plot). In real estate transactions, notation to two decimal places is standard, though integer calculations are practically sufficient for rough estimates.

Japanese real estate transactions have strict regulations regarding area display from a consumer protection perspective. The Real Estate Transaction Act and Fair Competition Code for Real Estate Advertising establish the following provisions. First, advertisements and property materials must include ㎡ notation. While tsubo notation is permitted alongside, ㎡ notation takes priority. Exclusive area (for condominiums) and land area must be clearly distinguished in display. Balconies and private gardens must not be included in exclusive area and must be listed separately. Building total floor area must display the sum of each floor's area. Additionally, misleading expressions (displays using only subjective expressions like "spacious") are prohibited. These regulations enable consumers to select real estate based on accurate information. Violations may result in penalties including business suspension under real estate transaction law violations.

The Building Standards Act regulates the scale of buildings that can be constructed relative to site area. These calculations use ㎡ units. Building coverage ratio is the ratio of building area (projected area when viewed from directly above) to site area. For example, with 100㎡ (approximately 30 tsubo) of land at 60% building coverage, maximum building area is 60㎡ (approximately 18 tsubo). Floor area ratio is the ratio of total floor area (sum of each floor's area) to site area. For example, with 100㎡ of land at 200% floor area ratio, maximum total floor area is 200㎡ (approximately 60 tsubo) for construction. This means a two-story building could have 100㎡ per floor, or a three-story building approximately 66.7㎡ per floor. These regulations are set with different values for each use district based on city planning law, established for purposes including urban landscape protection, securing sunlight rights, and disaster prevention. When constructing buildings, verification with the municipality's city planning department is always necessary.

In the real estate market, "price per tsubo" is frequently used when comparing land and building prices. Price per tsubo means the price for one tsubo, calculated as "total price ÷ number of tsubo = price per tsubo." For example, 30 million yen for 30 tsubo of land yields a price per tsubo of 1 million yen. Using price per tsubo makes it easier to compare price appropriateness even for properties with different areas. In urban residential areas, prices per tsubo are often 2 million yen or more, while suburbs typically range from 500,000 to 1 million yen. However, judging property value by price per tsubo alone is risky. Many factors affect price, including land shape (regular or irregular), road contact situation (length facing road), use district (residential or commercial), distance from station, and surrounding environment. For buildings, construction age, structure (wooden, steel frame, RC construction), and equipment grade must also be considered. Price per tsubo should be used as one indicator for property comparison, with comprehensive judgment being important.

The history of the tsubo unit is closely related to the development of Japan's weights and measures system. The shakkanhō measurement system introduced from China during the Nara period underwent unique Japanese development, with the tsubo area unit being established during the Edo period. It originated from defining one ken (6 shaku, approximately 1.818 meters) square as one tsubo, based on surveying techniques and architectural styles of that time. This corresponds to the area of two tatami mats and was naturally accepted as the basic unit of Japanese living space. During the Meiji era standardization of weights and measures, tsubo became an official legal unit, but was removed from legal units with the 1966 Measurement Act revision. However, it continues to be widely used as custom, particularly in the real estate industry. This is because tsubo is a unit rooted in Japanese people's sense of living, making it easy to imagine residential space. Hearing "30-tsubo house," many Japanese can picture a standard family home. From this cultural background, tsubo has become a symbolic presence representing Japanese residential culture beyond being merely a measurement unit.

Various area units are used in countries worldwide. The international standard ㎡ (square meters) is officially used in almost the entire world. In English-speaking countries like the United States and United Kingdom, square feet (sq.ft) are commonly used. One square foot is approximately 0.0929㎡, with one tsubo equivalent to approximately 35.58 square feet. In China and Taiwan, the character "坪" is used, but its size differs from Japan, with one 坪 being approximately 3.3㎡. In Korea, there is a unit called "평 (pyeong)" which is nearly the same size as Japanese tsubo. India uses square feet plus traditional units like "bigha" and "acre." European countries standardly use ㎡, though the UK also uses square feet concurrently. Because different area units are used in each country, conversion to ㎡ is essential for international real estate transactions. For foreigners purchasing real estate in Japan, the tsubo unit is difficult to understand, making ㎡ notation play an important role.

Using this conversion tool enables more accurate understanding of real estate information. Usage tips include: when viewing real estate advertisements, check both tsubo number and ㎡ to verify calculation accuracy. Occasionally incorrect conversions are displayed. Next, when considering home purchase or rental, knowing the necessary space for family composition in both tsubo and ㎡ makes property searching smoother. General guidelines suggest: for single living 15-20㎡ (approximately 4.5-6 tsubo), for couples 30-40㎡ (approximately 9-12 tsubo), for three-person families with one child 50-70㎡ (approximately 15-21 tsubo), and for four-person families with two children 70-90㎡ (approximately 21-27 tsubo) as comfortable space. When purchasing land, consider building coverage and floor area ratios to calculate actual buildable structure size in both tsubo and ㎡. Additionally, when rooms have tatami notation, confirming regional tatami size and converting to accurate ㎡ is important. Using this tool to calculate various patterns deepens real estate understanding and enables appropriate property selection.