Gallon-atmosphere (US) to kilocalories conversion calculator shown above calculates how many kilocalories are in 'X' gallon-atmosphere (US) (where 'X' is the number of gallon-atmosphere (US) to convert to kilocalories). In order to convert a value from gallon-atmosphere (US) to kilocalories (from gal atm to kcal) type the number of gal atm to be converted to kcal and then click on the 'convert' button.