Millimeters of mercury to decibars conversion calculator shown above calculates how many decibars are in 'X' millimeters of mercury (where 'X' is the number of millimeters of mercury to convert to decibars). In order to convert a value from millimeters of mercury to decibars (from mmHg to dbar) just type the number of mmHg to be converted to dbar and then click on the 'convert' button.