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