However, pixels are different sizes on different displays, so the answer is 58.74 pixels per inch on a 75-inch 4K television, ...

This gets you the recommended screen diagonal. If you're like most people ... If you have any doubts, try taping off or ...

What you'll need is the diagonal display size in inches and the resolution of the screen. Both of these numbers can be found on the technical specifications page of your display or device.