Centimeters of water to millibars converter above calculates how many millibars are in 'X' centimeters of water (where 'X' is the number of centimeters of water to convert to millibars). In order to convert a value from centimeters of water to millibars (from cmH2O to mbar) simply type the number of cmH2O to be converted to mbar and then click on the 'convert' button.