Barrels (US fluid) to gallons (UK) conversion calculator above calculates how many gallons (UK) are in 'X' barrels (US fluid) (where 'X' is the number of barrels (US fluid) to convert to gallons (UK)). In order to convert a value from barrels (US fluid) to gallons (UK) (from fl bl to gal) just type the number of fl bl to be converted to gal and then click on the 'convert' button.