Gigapascals to megabars conversion calculator shown above calculates how many megabars are in 'X' gigapascals (where 'X' is the number of gigapascals to convert to megabars). In order to convert a value from gigapascals to megabars (from GPa to Mbar) simply type the number of GPa to be converted to Mbar and then click on the 'convert' button.