Screen specs for 108 devices

It depends on viewing distance. A phone sits 20 cm from your eyes and needs over 400 ppi to hide the grid, while a 65" TV watched from 2 m is fine at 68 ppi. Every extra pixel costs battery and graphics power.

Neither works alone. The same 4K gives 163 ppi at 27", where text looks razor sharp, but only 80 ppi at 55", where pixels show up close. You always have to read both numbers together.

It is an Apple marketing name with no fixed number behind it. A display earns it when pixels stop being distinguishable at the distance you normally use it. That is why 326 ppi on a phone and 224 ppi on a MacBook share the label.

To keep a width that still fits one hand while growing the screen, the only direction left is up. That took phones from 16:9 to 19.5:9 and 20:9 — at the cost of black bars beside 16:9 video.

Only the resolution and the diagonal are written down. Density, aspect ratio, physical size and pixel pitch are all computed from those three numbers, and the computed density is checked against the figure the manufacturer publishes.