If you want the screen cm size to match the physical cm size, you'll want to use View > Print Size.
In order for it to work properly, calculate your screen resolution.
Horizontal Pixel Resolution divided by the the Horizontal Size of your screen, in my case 1280 pixels/11.25 inches = 114 ppi (you can use ppcm)
Go to Photoshop Preferences > Units and Rulers, and enter the new value in Screen Resolution. OK to confirm.
After that you can go to View > Print Size anytime and it will set the Zoom Level so that screen cm = physical cm.
