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