Inches of water to centimeters of water conversion calculator shown above calculates how many centimeters of water are in 'X' inches of water (where 'X' is the number of inches of water to convert to centimeters of water). In order to convert a value from inches of water to centimeters of water (from inH2O to cmH2O) type the number of inH2O to be converted to cmH2O and then click on the 'convert' button.