Centimeters of mercury to millibars conversion calculator above calculates how many millibars are in 'X' centimeters of mercury (where 'X' is the number of centimeters of mercury to convert to millibars). In order to convert a value from centimeters of mercury to millibars (from cmHg to mbar) type the number of cmHg to be converted to mbar and then click on the 'convert' button.