Barrels to Gallons Converter Type a value in the Barrels field to convert the value to Gallons: Barrels Gallons: How many gallons are there in a barrel? There are 42 gallons in a barrel. Barrels to Gallons Conversion Formula Gallons = Barrels * 42 I.e the volume in gallons is equal to the barrels value multiplied by 42. Barrels to Gallons Conversion Table Barrels Gallons 0 0 1 42 2 84 3 126 4 168 5 210 6 252 7 294 8 336 9 378 10 420 20 840 50 2100 100 4200 500 21000 1000 42000 2000 84000 Volume Measurements in the US Customary System US Customary Units of Volume Volume measures capacity occupied by liquid, solid, or gas. Gallons, quar...