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PPI Calculator

Pixel density from resolution and screen size, with the distance the pixels disappear.

What you provide

About 24 in for a desk monitor, 12 in for a phone.

Result

108.8 PPI

At 24 inches the pixels remain individually resolvable: 143 PPI would be needed and this panel has 109. Move back to 32 inches and they merge.

Diagnostic telemetry
Pixel density
108.8 PPI
Dot pitchCentre-to-centre spacing of two pixels
0.2335 mm
Panel size59.8 × 33.6 cm
23.5 × 13.2 in
Density needed at 24 in
143 PPI
Pixels invisible beyond80 cm — where individual pixels stop being resolvable
31.6 in

What this cannot tell you

  • Assumes square pixels and a flat panel measured corner to corner. A curved screen measured along the curve gives a slightly low density.
  • The "pixels disappear" distance uses 20/20 vision, which resolves about one arcminute. Acuity varies: someone with 20/12 vision resolves nearly twice the detail and will see structure this calculation says is invisible.
  • Density says nothing about panel quality. Contrast, colour accuracy, response time and coating all affect how a screen looks and none of them appear here.
  • Subpixel arrangement is not accounted for. Two panels at the same density can render text differently depending on whether they use a standard stripe layout or a pentile-style arrangement.

Take this with you

How this calculation works

Pixel density is the diagonal in pixels divided by the diagonal in inches — the two diagonals are the only dimensions that are directly comparable, which is why the calculation goes through them rather than through width. From the density everything else follows: dot pitch is the spacing between pixel centres, and the physical width and height come from the resolution treated as an aspect ratio. The "retina" figure is the same arcminute threshold used throughout this site: normal vision resolves detail about one sixtieth of a degree apart, so a pixel that subtends less than that cannot be distinguished from its neighbour at that distance.

What the results mean

PPI
Pixels per inch. Roughly 110 for a 27-inch 1440p monitor, 160 for a 27-inch 4K, and above 300 for a modern phone.
Dot pitch
The distance between the centres of two neighbouring pixels, in millimetres. The same measurement inverted — lower is sharper.
Density needed at this distance
The density at which pixels stop being individually resolvable at the distance you entered. Meeting it is what "retina" means.
Pixels invisible beyond
How far back you have to sit before this panel's pixel structure disappears. For a desk monitor, compare it with your actual seating distance.

Common problems and fixes

Text looks fuzzy despite a high PPI
That is usually scaling rather than density. A display running at a non-integer scale factor resamples text; try 100% or 200% scaling, and check the panel is at its native resolution.
Two monitors of the same size look different
Compare their densities here. A 27-inch 1440p panel and a 27-inch 4K panel differ by about 50% in density, which is visible immediately in text.
My phone density seems impossibly high
Phone panels genuinely run at 400–500 PPI. The relevant figure is the viewing distance: at 12 inches, the pixels are invisible well before that.

Frequently asked questions

What is a good PPI for a monitor?

At a typical desk distance of around 24 inches, roughly 140 PPI is where pixels stop being individually resolvable for normal vision. That makes a 27-inch 4K panel (about 163 PPI) comfortably past it, a 27-inch 1440p panel (about 109) noticeably short of it, and a 24-inch 1080p panel (about 92) clearly below. Below about 100 PPI most people see text edges at a desk.

What does "retina display" actually mean?

It is a claim about a distance, not a fixed density. It means the pixels are small enough that at the intended viewing distance they subtend less than about one arcminute — the finest detail normal vision resolves. That is why a phone needs over 300 PPI to qualify and a television at three metres needs barely 60: the same threshold, applied at different distances.

Is higher PPI always better?

Only up to the point where the pixels are already invisible at your viewing distance. Past that, extra density costs GPU performance and battery life and buys nothing you can see. Contrast, colour accuracy and refresh rate all continue to matter after density has stopped.

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