Area is a physical quantity that expresses the size of the extent of plane figures or curved surfaces in numbers. It is used to measure the size of land, floor areas in buildings, and room sizes. Different area units are used depending on country, region, and purpose, and accurate conversion is necessary.
Metric Area Units
In the metric system based on the International System of Units (SI), area units are defined based on the length unit - the meter.
Square meter (m² / square meter)
The area of a square with sides of 1 meter. The world standard area unit, also used as the legal standard unit in most countries. Square meters are used in official documents such as real estate registration and building permits. '1m² = 1m × 1m'. A typical 6-tatami room (Japanese) is approximately 10m², a tennis court is approximately 260m².
Hectare (ha / hectare)
The area of a square with sides of 100 meters. 1 hectare = 10,000 square meters. Used mainly for agricultural land, forests, and large plots of land. 'One Tokyo Dome' is approximately 4.7 hectares, 'a 1-hectare rice field' means 100m × 100m. One hundredth of a hectare is 'are (a)', where 1a = 100m².
Square kilometer (km² / square kilometer)
The area of a square with sides of 1 kilometer (1,000 meters). 1km² = 1,000,000m² = 100 hectares. Used to express areas of cities and countries. 'The area of Tokyo's 23 wards is approximately 627km²' and 'Japan's area is approximately 377,975km²' are typical expressions.
Traditional Japanese Area Units
Tsubo (つぼ / tsubo)
Traditional Japanese area unit, 1 tsubo ≈ 3.30579 square meters. Equivalent to the area of two tatami mats (1 tsubo ≈ 2 tatami). Originally defined as the area of a square of 1 ken (approximately 1.818m) × 1 ken. Still widely used in the Japanese real estate industry, expressions like '30-tsubo plot' and '100-tsubo house' are common. Although square meters are the legal measurement, tsubo remains widely accepted.
Tatami (じょう / jo)
Unit representing the area of one tatami mat. 1 tatami ≈ 1.65 square meters (varies by region). 'A 6-tatami room' is approximately 10 square meters, approximately 3 tsubo. However, tatami size varies by region, with standards like Kyoma, Edoma, and apartment sizes. Designations like '6 tatami' and '8 tatami' are used in real estate floor plans.
Imperial Area Units
Traditional unit system used primarily in the United States and United Kingdom.
Square foot (ft² / square foot)
The area of a square with sides of 1 foot (approximately 30.48 cm). 1 square foot ≈ 0.0929 square meters. In American real estate, expressions like '1,500 sqft apartment' are common, which is approximately 139 square meters. Symbols: 'sq ft', 'sqft', 'ft²'.
Acre (ac / acre)
Unit used primarily to express land area. 1 acre = 4,840 square yards = 43,560 square feet ≈ 4,047 square meters. Used for agricultural land and large plots. 'A 100-acre farm' is approximately 40 hectares.
Square mile (mi² / square mile)
The area of a square with sides of 1 mile (approximately 1.609 km). 1 square mile ≈ 2.59 square kilometers = 259 hectares = 640 acres. Used to express areas of cities and countries. 'New York City's area is approximately 302 square miles' is a typical expression.