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PPI Calculator Pixel density from resolution and size

Enter a screen’s resolution and diagonal to get pixels per inch, dot pitch and the panel’s real width and height.

Diagonal in inches or centimeters
Dot pitch and physical size included
Shows the distance where pixels blend together

Built by Marcus Reed, laptop and desktop repair technician

PPI calculatorPPI = √(w² + h²) ÷ diagonal

Horizontal pixelsFirst number of the resolution

Vertical pixelsSecond number of the resolution

Diagonal sizeAs advertised

Pixel density

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Uses the advertised diagonal, which is often rounded, so the result can differ slightly from the maker’s spec sheet.

91.79PPI on a 24-inch 1080p monitor
108.79PPI on a 27-inch 1440p monitor
163.18PPI on a 27-inch 4K monitor
25.4 mmin an inch; dot pitch = 25.4 ÷ PPI

Quick answer

PPI, or pixels per inch, is the number of pixels along the screen’s diagonal divided by the diagonal size in inches. A 27-inch monitor at 2560 x 1440 works out to about 109 PPI, a 24-inch 1080p monitor to about 92, and a 27-inch 4K monitor to about 163. Enter any resolution and size in the calculator above.

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The PPI formula

First find the diagonal in pixels with the Pythagorean theorem: the square root of width squared plus height squared. Then divide by the diagonal size in inches. For 2560 x 1440, the diagonal is about 2,937 pixels; across 27 inches that is 108.79 pixels per inch. The calculator also uses the PPI to work back to the screen’s real width and height, which helps when you’re checking whether a monitor fits a desk or a laptop fits a bag.

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PPI of common screens

Screen	Resolution	PPI
24-inch 1080p monitor	1920 × 1080	91.79
27-inch 1080p monitor	1920 × 1080	81.59
27-inch 1440p monitor	2560 × 1440	108.79
32-inch 1440p monitor	2560 × 1440	91.79
27-inch 4K monitor	3840 × 2160	163.18
32-inch 4K monitor	3840 × 2160	137.68
34-inch ultrawide	3440 × 1440	109.68
14-inch 1080p laptop	1920 × 1080	157.35
15.6-inch 1080p laptop	1920 × 1080	141.21
14-inch 1920 × 1200 laptop	1920 × 1200	161.73

Notice that a 32-inch 1440p monitor has the same pixel density as a 24-inch 1080p one. Bigger at the same resolution means each pixel is larger, not that the picture is sharper.

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How far away do the pixels disappear?

PPI alone doesn’t tell you whether a screen looks sharp; distance does the rest. A common yardstick is 20/20 vision, which corresponds to making out detail about one arcminute across, a sixtieth of a degree. Past the distance where one pixel shrinks below that angle, a person with 20/20 vision can no longer pick out single pixels. The calculator shows that distance for any screen as “pixels blend from about”. The figure is 3,438 divided by the PPI, in inches:

Screen	PPI	Pixels blend from about
24-inch 1080p monitor	91.79	37.5 in (95 cm)
27-inch 1440p monitor	108.79	31.6 in (80 cm)
34-inch 3440 × 1440 ultrawide	109.68	31.3 in (80 cm)
32-inch 4K monitor	137.68	25.0 in (63 cm)
27-inch 4K monitor	163.18	21.1 in (54 cm)
15.6-inch 1080p laptop	141.21	24.3 in (62 cm)
14-inch 1080p laptop	157.35	21.8 in (55 cm)

Measure from your eyes to the screen where you sit now. If you’re closer than the figure for a monitor you’re considering, you’ll see the pixel grid and text edges will look soft; a 24-inch 1080p screen at a typical arm’s-length desk distance is the usual example. If you’re already farther away, paying for more PPI buys little you can see.

This explains a common r/Monitors complaint. In a 2026 thread with 190 upvotes, someone who went from a 27-inch 1440p monitor to a 32-inch 4K one wrote that they had “yet to be wowed.” The calculator shows why: 108.79 to 137.68 PPI is a 27% step, and the blend distance only moves from about 32 inches to 25. At a normal desk distance, part of that extra detail is already past what the eye resolves, while the graphics card pays for every one of the extra pixels.

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What Windows scaling does with a high-PPI screen

Microsoft’s guidance on high-DPI displays says almost all desktop monitors and most laptop screens sit around 95 to 110 DPI, where Windows uses 100% scaling, and that sharper panels get higher scale factors so text stays a comfortable size. Scaling makes everything bigger, so the amount of desktop you can fit on screen shrinks to the resolution divided by the scale:

Screen	Scale	Desktop space it gives
27-inch 4K	150%	2560 × 1440
27-inch 4K	125%	3072 × 1728
15.6-inch 1080p laptop	125%	1536 × 864
14-inch 1920 × 1200 laptop	150%	1280 × 800

That first row is the practical answer to “27-inch 1440p or 27-inch 4K?”. At 150%, the 4K screen fits the same amount of desktop as the 1440p one, with text drawn from 2.25 times as many pixels, so it looks crisper. Choose 1440p if you’d rather put the money elsewhere or need the graphics card to run games at full resolution. One r/Monitors owner who bought 4K for gaming wrote that they were “BLOWN AWAY at how much clearer text is,” coming from 1440p. For reading and spreadsheets, that is the difference you pay for. Microsoft explains the scale factors on its high DPI and Windows page.

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Choosing a resolution for a screen size

Pixel density only matters in relation to how far away you sit, which is why a TV can look sharp at a much lower PPI than a phone. For a desk monitor at normal distance, the jump from 1080p to 1440p at 27 inches is easy to see in text. At 4K, Windows display scaling keeps text a readable size, so you get sharper letters rather than smaller ones.

Shape matters as much as sharpness: the aspect ratio calculator shows how tall a screen is for its width. If you’re building a gaming PC to drive a high-resolution screen, the gaming PC build guide covers checking that the parts fit each other and getting a picture on the first power-on.

FAQ

Questions people ask

What is the PPI of a 27-inch 1440p monitor?

About 108.79 PPI. The diagonal of 2560 x 1440 is about 2,937 pixels, and 2,937 divided by 27 inches is 108.79.

Is higher PPI always better?

Higher PPI makes text and edges sharper at the same distance, but Windows has to scale the interface up so it stays readable, and some older apps look blurry when scaled. It also takes more graphics power to run games at the full resolution.

What is the difference between PPI and DPI?

PPI counts pixels per inch on a screen. DPI counts printed dots per inch on paper. People often use DPI for screens too, but for a monitor or laptop the right term is PPI.

What is dot pitch?

Dot pitch is the distance from one pixel to the next, usually in millimeters. It is 25.4 divided by the PPI, so a smaller dot pitch means a sharper screen.

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