first, you define the resolution of your display

or skip to
the result
chart→
| width in pixel | height in pixel |
| diameter in inch |
now move away from Display, until you
cant differ pixels.Measure the Distance.
| enter your Distance in centimeters |
Display Sizes and Resolution, you're at least able to differ | |
| Example configurations with 1920*1080 | you're able to differ |
| (92ppi) 24" Display @80cm distance | |
| (60ppi) 37" Display @2.5m distance | |
| (48ppi) 46" Display @3.5m distance | |
| (44ppi) 50" Display @4.5m distance | |