Retina Display Calculator
Work out whether a screen is "Retina" — sharp enough that you can't pick out individual pixels — at the distance you actually sit from it. Enter the resolution, diagonal size, and viewing distance, and the calculator returns the pixel density, the pixels per degree your eye sees, and a clear pass or fail against the limit of 20/20 vision.
Below the eye's resolving limit at this distance — pixels blend into a continuous image. It stays Retina from about 21.1" · 53.5 cm and farther.
"Retina" is Apple's marketing name for a screen whose pixels are too small to make out individually at a normal viewing distance — there is no single fixed spec behind it. It rests on human visual acuity: a person with 20/20 vision can just resolve detail about one arcminute (1/60 of a degree) apart. Once each pixel subtends a smaller angle than that, the eye blends the grid into a continuous image. "HiDPI" is the vendor-neutral term for the same class of high-density displays.
Sharpness is angular, not absolute, so distance is half the equation. From your resolution and diagonal the calculator derives the pixel density (PPI), then combines it with your distance to get pixels per degree (PPD) — how many pixels fall within one degree of your field of view, roughly PPI × distance(inches) × π/180. Around 60 PPD is one pixel per arcminute, where the average eye stops resolving the grid, so the verdict is a pass or fail against that ~60 PPD threshold. The stat tiles add the arcminutes per pixel, the "Retina distance" where your screen crosses the line, and the PPI a panel would need to be Retina where you sit.
Keep PPI and PPD apart. Pixel density (PPI) is fixed by the panel — resolution divided by physical size. Pixels per degree (PPD) is what your eye receives, and it depends on how far back you sit. A 460 PPI phone and an 80 PPI TV can both be Retina, because you hold the phone a foot away and sit two metres from the TV — and since PPD rises as you move back, every display is "Retina" at some distance. So the useful question is never the raw PPI, but whether the screen clears ~60 PPD where you actually use it.
Common devices at a glance
| Display | Pixel density | Typical distance | Retina verdict |
|---|---|---|---|
| Modern smartphone | ~400–500 PPI | 10–14 in | Comfortably Retina (~85–100 PPD) |
| MacBook Air / Pro | ~224–254 PPI | 18–24 in | Retina in normal use (~75–90 PPD) |
| 27-inch 4K monitor | ~163 PPI | ~24 in | Just clears the bar (~68 PPD) |
| 27-inch 1440p monitor | ~109 PPI | ~24 in | Sharp, but short of Retina (~46 PPD) |
| 55-inch 4K television | ~80 PPI | ~8 ft | Easily Retina at couch distance (~130 PPD) |