The rai equals 1600 square metres exactly — the traditional Thai land unit. It is 1/6.25 of a hectare. Still widely used in Thai property transactions and agricultural documents. A rai is subdivided into 4 "ngan" (400 m² each).
Real-world: A small Thai farm might be 10–20 rai (1.6–3.2 ha). Thai rice yields: 400–600 kg per rai.
Read full rai reference →The acre equals 4046.86 square metres — originally the area a team of oxen could plough in a day. It is the standard rural land unit in the US, UK and Canada. Suburban American lots are typically a quarter to half an acre. 640 acres equal one square mile.
Real-world: A US suburban lot is 0.25–0.5 acre. A standard UK rural property might be 5 acres. A football pitch is about 1.8 acres.
Read full acre reference →