Firkin

Imperial (British)Traditional unit (still used in some regions)

9 imperial gallons (40.9 L), a quarter of a barrel. A traditional cask size for beer.

1 firkin = 40.91481 liters (exactly).

About the firkin

Probably from Middle English ferdekyn, which in turn likely comes from a Middle Dutch diminutive of vierde, fourth, the firkin is literally a little quarter: a quarter of a barrel. For beer in Britain that means 9 imperial gallons, about 41 liters (40.9 L here), or 72 imperial pints.

The word has been used for other goods too. A wine firkin was much bigger, at 70 imperial gallons by one reckoning, while British butter and cheese were sold by the firkin of 56 pounds, about 25 kilograms. An American dry firkin of 9 US gallons is only about 34 liters, and the word could also mean any small wooden tub for butter, lard or fish. Authors such as William Robinson in 1825 treated it as a recognised trade measure.

Sources: Wikipedia: Firkin (unit); Wikipedia: Barrel (unit); Wikipedia: Cask ale

Firkin conversion chart

1 firkin expressed in every other volume unit:

More Imperial (British) units

• imperial gallon (volume)
• imperial quart (volume)
• imperial pint (volume)
• imperial gill (volume)
• imperial fluid ounce (volume)
• UK beer barrel (volume)
• kilderkin (volume)
• hogshead (ale) (volume)
• stone (weight & mass)
• long ton (weight & mass)
• hundredweight (UK) (weight & mass)
• quarter (UK) (weight & mass)
• fortnight (time)
• score (time)
• furlong per fortnight (speed)
• poundal (force)

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