This depends on the size of the barrel as there are many different sizes in use around the world.

- A barrel is a hollow cylindrical container, most commonly used to carry liquids or foodstuffs. It consists of multiple wooden boards, held together by metal or wooden hoops which are placed at the top, middle and bottom. Kegs are smaller versions of barrels and can be wooden or a pressurized aluminum container

- A United Kingdom beer barrel contains exactly 36 imperial gallons of beer. This equates to 43 US gallons, or 164 litres. A United States standard beer barrel contains 31.5 US gallons which equates to 26 imperial gallons or 119 litres. A keg, whether of traditional wooden or aluminum construction, holds 15.5 gallons of beer.

- An imperial gallon is divisible into fluid ounces and this will measurement will be utilised in this answer. There are 160 fluid ounces in 1 imperial gallon and there are 12 fluid ounces ounces per glass which is equal to 12/160 or 0.075 imperial gallons.

- For a UK barrel of beer, half of 36 imperial gallons is 18 gallons. Therefore, the number of glasses is 18 ÷ 0.075 = 240 glasses.

- For a US barrel, half of 26 imperial gallons is 13 gallons. Therefore the number of glasses is 13 ÷ 0.075 = 173.3 glasses.

- A barrel is a hollow cylindrical container, most commonly used to carry liquids or foodstuffs. It consists of multiple wooden boards, held together by metal or wooden hoops which are placed at the top, middle and bottom. Kegs are smaller versions of barrels and can be wooden or a pressurized aluminum container

- A United Kingdom beer barrel contains exactly 36 imperial gallons of beer. This equates to 43 US gallons, or 164 litres. A United States standard beer barrel contains 31.5 US gallons which equates to 26 imperial gallons or 119 litres. A keg, whether of traditional wooden or aluminum construction, holds 15.5 gallons of beer.

- An imperial gallon is divisible into fluid ounces and this will measurement will be utilised in this answer. There are 160 fluid ounces in 1 imperial gallon and there are 12 fluid ounces ounces per glass which is equal to 12/160 or 0.075 imperial gallons.

- For a UK barrel of beer, half of 36 imperial gallons is 18 gallons. Therefore, the number of glasses is 18 ÷ 0.075 = 240 glasses.

- For a US barrel, half of 26 imperial gallons is 13 gallons. Therefore the number of glasses is 13 ÷ 0.075 = 173.3 glasses.