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