About these units
square meter (m²)
A square meter (m²) is the area of a square 1 m on each side. It is the legal unit for floor area in most countries.
pyeong / tsubo
The pyeong is the area of a square 6 shaku (about 1.818 m) on each side, 400/121 m² or about 3.3058 m². Koreans still use it for homes and land, though official documents use square meters. The Japanese tsubo (坪) is the same size.