How to calculate Design Pressure, when Working pressure is known for Unfired Pressure Vessel like Boiler, Reactor and Storage Tank, etc?

Design pressure can be calculated by adding 5 - 10% in working pressure.

For Example: If Working Pressure of Reactor is 5 Kgf, then what is the Design pressure to take in calculation for Reactor (Unfired Pressure Vessel)?

Solution: Working Pressure = 5 Kgf

                Design Pressure   = 5 Kgf + 5%

                                               = 5 Kgf + 0.25 Kgf

                                               = 5.25 Kgf