Megabars to atmospheres (standard) conversion calculator above calculates how many atmospheres (standard) are in 'X' megabars (where 'X' is the number of megabars to convert to atmospheres (standard)). In order to convert a value from megabars to atmospheres (standard) (from Mbar to atm) just type the number of Mbar to be converted to atm and then click on the 'convert' button.