Tun (unit)

The tun ( ang, tunne, la, tunellus, ) is an English unit of ''liquid volume'' (not weight), used for measuring wine, oil or honey. Typically a large vat or vessel, most often holding 252 wine gallons, but occasionally other sizes (e.g. 256, 240 and 208 gallons) were also used. The modern tun is about 954 litres.

The word ''tun'' is etymologically related to the word ''ton'' for the unit of mass, the mass of a tun of wine being approximately one long ton, which is .

History

Originally, the tun was defined as 256 wine gallons; this is the basis for the name of the quarter of 64  corn gallons. At some time before the 15th century, it was reduced to 252 gallons, so as to be evenly divisible by other small integers, including seven.252 = 

In one Early Modern English example from 1507, a tun is defined as 240 gallons.

With the adoption of the Queen Anne wine gallon of 231 cubic inches in 1706 the tun approximated the volume of a cylinder with both diameter and height of 42 inches.The volume, ''V'', of this cylinder may be approximated from the height, ''h'', and the radius, ''r'', as follows.
: These were adopted as the standard US liquid gallon and tun.

When the imperial system was introduced in 1824 the tun was redefined in the UK and colonies as 210 imperial gallons. The imperial tun remained evenly divisible by small integers.210 =  There was also little change in the actual value of the tun.The imperial tun is only about % larger than the US tun assuming current definitions. Note that .

Standard tuns of wine came to serve as a measure of a ship's capacity.. "Historically, a very important and standard cargo for European sailing vessels was wine, stored and shipped in casks called tuns. These tuns of wine, because of their uniform size and their universal demand, became a standard by which a ship's capacity could be measured. A tun of wine weighed approximately 2,240 pounds, and occupied nearly 60 cubic feet." ( Gillmer, Thomas (1975). ''Modern Ship Design''. United States Naval Institute.) "Today the ship designers standard of weight is the long ton which is equal to 2,240 pounds."

Definitions

In the US customary system, the tun (symbol: US tu) is defined as 252 US fluid gallons (about ).

In the imperial system, the tun is defined as 210 imperial gallons (about ).

Conversions

Both the imperial and US tuns were subdivided into smaller units as follows.

Explanatory notes

References

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Customary units of measurement
Units of volume