Question: one barrel of beer is how many gallons?
Answer: Fluid barrel in the US and UK In the US most fluid barrels (apart from oil) are 31.5 US gallons (26 imp gal; 119 L) (half a hogshead), but a beer barrel is 31 US gallons (26 imp gal; 117 L). The size of beer kegs in the US is based loosely on fractions of the US beer barrel.