Pounds per square inch to inches of water conversion calculator shown above calculates how many inches of water are in 'X' pounds per square inch (where 'X' is the number of pounds per square inch to convert to inches of water). In order to convert a value from pounds per square inch to inches of water (from psi to inH2O) just type the number of psi to be converted to inH2O and then click on the 'convert' button.