🖥️ Displays

Screen Resolution PPI Calculator

Find any display's pixel density from its resolution and diagonal size, plus pixel pitch, megapixels, physical dimensions and the viewing distance at which the pixels stop being visible. Press Calculate.

Written and reviewed by SM Arijul Islam · Last reviewed 29 October 2026 · Editorial standards · Report an error

How PPI is calculated

Pixels per inch is the number of pixels packed into one inch of the panel. Take the pixel diagonal, which is the square root of width squared plus height squared, and divide it by the physical diagonal measured in inches. A 1920 × 1080 screen has a pixel diagonal of 2,203.6, so a 24 inch monitor gives 2,203.6 ÷ 24 = 91.8 PPI.

Pixel pitch is the same fact stated the other way round: the distance from the centre of one pixel to the next, in millimetres. It is simply 25.4 ÷ PPI, so the same 24 inch monitor has a pitch of about 0.277 mm. Higher PPI means a finer image at the same distance.

Reference values

Common devices and their pixel density
Device	Resolution	Size	PPI
1080p monitor	1920 × 1080	24 in	91.8
1440p monitor	2560 × 1440	27 in	108.8
4K monitor	3840 × 2160	27 in	163.2
4K television	3840 × 2160	55 in	80.1
Ultrawide	3440 × 1440	34 in	109.7
1080p laptop	1920 × 1080	15.6 in	141.2
Tablet	2732 × 2048	12.9 in	264.7
Phone	1179 × 2556	6.1 in	460.6

How close can you sit?

Human vision resolves about one arcminute of angle. When a pixel is smaller than that angle at your seating distance, the eye can no longer separate neighbouring pixels and the image looks continuous — the idea behind Apple's "Retina" marketing. Converted to a rule of thumb, the distance where a pixel subtends one arcminute in centimetres is roughly 344 × pixel pitch in millimetres.

A 24 inch 1080p screen at 0.277 mm pitch merges into a continuous image beyond about 95 cm.
A 27 inch 4K screen at 0.156 mm pitch looks smooth from about 54 cm.
A phone at 0.055 mm pitch is effectively perfect from about 19 cm, which is closer than anyone holds a phone.

Worked examples

2560 × 1440 on 27 inches: pixel diagonal √(2560² + 1440²) = 2,937.2, so 2,937.2 ÷ 27 = 108.8 PPI.
The same resolution on a 31.5 inch panel drops to 93.2 PPI, and the pixels are visibly larger.
3440 × 1440 on 34 inches gives 109.7 PPI — very close to a 1440p 27 inch monitor, which is why they feel similar.
A 55 inch 4K TV is only 80.1 PPI, which is plenty at a three metre sofa distance but poor as a desktop monitor.

Frequently asked questions

Is PPI the same as DPI?

Not quite. PPI counts pixels in a screen; DPI counts dots of ink a printer can place in an inch of paper. Screens are described with PPI, printers with DPI, and operating systems often use DPI to mean a UI scale factor.

Does a higher PPI make text sharper?

Up to a point, yes, as long as the software scales text to match. At very high densities the limiting factor becomes the font hinting and the size of the letters rather than the panel.

Why does my operating system use 150% scaling?

Because a high pixel density makes interface elements physically tiny. Scaling by 150% keeps a 163 PPI monitor usable at the same apparent size as a 109 PPI one, while keeping the extra sharpness.

Do TVs need a high PPI?

No. Viewing distance matters more than density: 80 PPI is excellent from three metres away, but a desktop monitor at 60 cm needs considerably more.

Common mistakes to avoid

Measuring the screen's visible width instead of the diagonal.
Ignoring viewing distance. Pixel density alone says nothing about how sharp a display looks in use.
Comparing PPI between a phone and a monitor as if they were used the same way.
Assuming a bigger number is always better. Past the retina distance, extra density is hard to see and costly in performance.

Sources and standards

CSS defines one reference pixel as 1/96 inch, which is why a browser reports a nominal DPI regardless of the physical panel. The W3C CSS Values specification fixes that ratio; the physical pixel density on this page is calculated from the panel's real dimensions and is a different number.