Gigawatt hours to megacalories conversion calculator above calculates how many megacalories are in 'X' gigawatt hours (where 'X' is the number of gigawatt hours to convert to megacalories). In order to convert a value from gigawatt hours to megacalories (from GWh to Mcal) type the number of GWh to be converted to Mcal and then click on the 'convert' button.