Joules to gallon-atmosphere (US) converter on this page calculates how many gallon-atmosphere (US) are in 'X' joules (where 'X' is the number of joules to convert to gallon-atmosphere (US)). In order to convert a value from joules to gallon-atmosphere (US) (from J to gal atm) simply type the number of J to be converted to gal atm and then click on the 'convert' button.