Mega-electron volts to nanojoules conversion calculator shown above calculates how many nanojoules are in 'X' mega-electron volts (where 'X' is the number of mega-electron volts to convert to nanojoules). In order to convert a value from mega-electron volts to nanojoules (from MeV to nJ) simply type the number of MeV to be converted to nJ and then click on the 'convert' button.