Gigabars to millimeters of mercury converter on this page calculates how many millimeters of mercury are in 'X' gigabars (where 'X' is the number of gigabars to convert to millimeters of mercury). In order to convert a value from gigabars to millimeters of mercury (from Gbar to mmHg) simply type the number of Gbar to be converted to mmHg and then click on the 'convert' button.