Giga-electron volts to megajoules conversion calculator above calculates how many megajoules are in 'X' giga-electron volts (where 'X' is the number of giga-electron volts to convert to megajoules). In order to convert a value from giga-electron volts to megajoules (from GeV to MJ) type the number of GeV to be converted to MJ and then click on the 'convert' button.