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