Photoshop's "print size" is still not accurate despite changed settings (Photoshop won't use decimals?)

To get the Print Size functionality to show the physical size of a print document on screen, follow these steps:

1. Let w be the width of your screen in cm (obviously you need to measure this with a ruler).

2. Let x be the width of your screen in pixels (find this in your display settings)

3. Screen resolution = x / w. Round the value to the nearest two decimal places. This should be accurate enough.

4. Create a new print document using the print presets in Photoshop, something like an A4 sheet will do. Make sure you set the units to centimetres, and the resolution to 118.11 pixels per centimetre (equivalent to 300ppi).

5. Go into Preferences > Units and Rulers, set the screen resolution you calculated in step 3, in pixels per centimetre. The print resolution setting should be 118.11 pixels per centimetre.

Now try View > Print Size. Then, with a ruler, measure the width of the sheet on screen. It should be 21cm.

Note: for consistency and to avoid confusion I made all measurements metric, however you can also use imperial measurements if you want. It makes no difference.