Design Pressure Calculations (DPC) is a calculation that identifies the load – induced by wind and/or static snow – a building and its openings must withstand in its end-use application. On the other hand, the manufacturer provides the Design Pressure Rating (DPR) which identifies the pressure that the window can withstand. It will tell you how well your windows or doors will stand up to high winds or heavy snow. The higher the DPR the stronger the window or door. DPR has to be equal or greater than DPC, in that way your windows /doors will be capable to support the local loads.