Centimeters of mercury to inches of water conversion calculator shown above calculates how many inches of water are in 'X' centimeters of mercury (where 'X' is the number of centimeters of mercury to convert to inches of water). In order to convert a value from centimeters of mercury to inches of water (from cmHg to inH2O) type the number of cmHg to be converted to inH2O and then click on the 'convert' button.