A ''rai'' ( th, ไร่, ) is a unit of
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while ''surface area'' refers to the area of an open su ...
equal to 1,600
square metres (16
ares
Ares (; grc, Ἄρης, ''Árēs'' ) is the Greek god of war and courage. He is one of the Twelve Olympians, and the son of Zeus and Hera. The Greeks were ambivalent towards him. He embodies the physical valor necessary for success in war ...
, 0.16
hectare
The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...
s, 0.3954
acre
The acre is a unit of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one furlong (66 by 660 feet), which is exactly equal to 10 square chains, of a square mile, 4,840 square ...
s), and is used in measuring land area for a
cadastre
A cadastre or cadaster is a comprehensive recording of the real estate or real property's metes-and-bounds of a country.Jo Henssen, ''Basic Principles of the Main Cadastral Systems in the World,'/ref>
Often it is represented graphically in a cad ...
or cadastral map.
Its current size is precisely derived from the
metre
The metre ( British spelling) or meter ( American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its p ...
, but is neither part of nor recognized by the modern
metric system
The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Intern ...
, the
International System (SI).
The rai is defined as 1 square ''sen'' or (40 m × 40 m). It can be divided in four ''
ngaan
A ngan ( th, งาน, , ) is a unit of area, equal to 400 square metres (20 m × 20 m), used for measuring land or property area. Its current size is precisely derived from the metre, but is neither part of nor recognized by the modern metric sys ...
'' or 400 square ''
wa''.
It is commonly used in
Thailand
Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...
. Although recognized by the SI, its use is not encouraged. The word ''rai'' also means
plantation
A plantation is an agricultural estate, generally centered on a plantation house, meant for farming that specializes in cash crops, usually mainly planted with a single crop, with perhaps ancillary areas for vegetables for eating and so on. Th ...
.
See also
*
Thai units of measurement
*
Orders of magnitude (area)
References
External links
Area metric conversion British and U.S., Japanese, Chinese, Thai, old French, others.
{{DISPLAYTITLE:''Rai'' (unit)
Units of area
Thai units of measurement