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PPI calculator

Compute the pixel density (PPI) of a screen from its resolution and size.

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Need Pixel density (PPI), Dot pitch (mm)? The PPI calculator derives it from Horizontal pixels, Vertical pixels, Diagonal (inches) in one step. For instance, with Horizontal pixels = 1,920, Vertical pixels = 1,080 and Diagonal (inches) = 24 it returns Pixel density (PPI) = 91.788 and Dot pitch (mm) = 0.277.

How to use it

  1. Enter your values: Horizontal pixels, Vertical pixels, Diagonal (inches).
  2. Read the result instantly: Pixel density (PPI), Dot pitch (mm).

Frequently asked questions

How does the PPI calculator work?

It takes Horizontal pixels, Vertical pixels and Diagonal (inches) and derives Pixel density (PPI) and Dot pitch (mm) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

3 values: Horizontal pixels, Vertical pixels and Diagonal (inches). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Horizontal pixels = 1,920, Vertical pixels = 1,080 and Diagonal (inches) = 24, the calculator returns Pixel density (PPI) = 91.788 and Dot pitch (mm) = 0.277. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

When would I actually use this?

Finding out how big a thing will be before you make it: how many gigabytes an hour of footage takes, how long a file needs on the connection you have, how large a photo prints before it goes soft, what bitrate fits the budget you were given.

What is the most common mistake?

Taking the advertised connection speed as the transfer speed. A 100 Mb/s line is megabits, the file is in megabytes, and the eight-fold difference between them is where most download estimates go wrong — before overhead and contention take their own share.

What is the difference between the PPI calculator and the Screen size calculator?

This one returns Pixel density (PPI) and Dot pitch (mm); the Screen size calculator returns Width (cm) and Height (cm). That is the whole difference — open the one whose figure you need.

Where do the figures come from, and how current are they?

Byte prefixes follow the IEC convention where a kibibyte is 1 024 bytes and a kilobyte is 1 000 — drive makers use the second, operating systems often report the first, and a disk that shrinks on arrival is that gap and nothing else. Print sizing assumes 300 dpi unless you change it.

Further reading

All guides →
ExplainerWhat Are PPI and DPI? Pixel Density for Screen and PrintPPI and DPI both measure density per inch, but one is about screens and the other about print. Learn how to compute pixel density and what Retina really means.ExplainerDPI, PPI, and What Actually Controls Print SizeThe DPI figure inside an image file is a label. It changes no pixels. Printed size is pixels divided by PPI — and DPI, properly used, means something else entirely: the printer's dots.ExplainerScreen Resolutions Explained: 1080p, 1440p, 4KWhat 1080p, 1440p, and 4K really mean. Learn how resolution counts pixels, why total pixels grow so fast, and how aspect ratio ties width to height.ExplainerFrame Rates, Timecode, and the Drop-Frame That Drops NothingFrames = duration × rate is trivial until the rate is 29.97. Non-drop timecode then drifts exactly 3.6 seconds an hour. Drop-frame corrects it by skipping 108 frame numbers — the same 108 — but the correction is not perfect: counting every frame shows a residual of 3.6 milliseconds per hour.ExplainerHow Big Is That Audio File?Uncompressed audio size is exact arithmetic: sample rate × bit depth × channels × seconds ÷ 8. CD audio is 176,400 bytes per second. A 320 kbps MP3, by contrast, is bitrate × duration and does not depend on the sample rate at all — 2,400,000 bytes a minute whether it came from 44.1 or 48 kHz.ExplainerScreen Resolution, Pixel Density, and the Numbers Marketing UsesA diagonal plus an aspect ratio gives you width and height by Pythagoras, and the answer is not what the marketing implies: a 27-inch 21:9 has 16.2% less area than a 27-inch 16:9. Then pixels per degree, which shows the highest-PPI phone is not the sharpest thing you own.