Amazon Kindle Paperwhite 3

Pixel pitch (computed from PPI; a rectangular estimate, not a measured panel pitch)

84.6 um

Physical size (computed from the rectangle, not the usable area)

4.82 by 3.57 in (12.2 by 9.1 cm)

Aspect ratio (computed)

1.35:1

Megapixels (computed)

1.55

Looks sharp from (assuming 20/20 vision, one pixel per arcminute)

11.4 in and further

Pixels per degree at an assumed 14 in viewing distance

73.4

Every row above is computed here from the stated resolution and the stated diagonal. With w and h in pixels and the diagonal in inches: PPI = sqrt(w^2 + h^2) / diagonal, which here is sqrt(1448^2 + 1072^2) / 6; pixel pitch = 25.4 mm / PPI; physical size = pixels / PPI, which is the full panel rectangle and not the usable area, so a screen with rounded corners or a notch has less usable area than the size shown; sharpness distance = 1 / (PPI x tan(1/60 degree)), the distance at which one pixel spans one arcminute for 20/20 vision; pixels per degree = 2 x distance x tan(0.5 degree) x PPI at the assumed viewing distance. Values are rounded to two decimals, and to one decimal for the pitch, the sizes in centimeters, the distances, and the pixels per degree.