Gigacalories to gigajoules converter above calculates how many gigajoules are in 'X' gigacalories (where 'X' is the number of gigacalories to convert to gigajoules). In order to convert a value from gigacalories to gigajoules (from Gcal to GJ) simply type the number of Gcal to be converted to GJ and then click on the 'convert' button.