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