Screen Size / PPI Calculator
Enter any three of width, height, diagonal, and PPI to solve for the rest — and compare two screens side by side.
Last updated
How to calculate a screen’s PPI
- Pick a device preset, or enter the screen’s width and height in pixels.
- Enter the diagonal size in inches; any three values solve for the fourth.
- Add a viewing distance to see pixels per degree, and fill in the second screen to compare.
About this tool
PPI (pixels per inch) is the diagonal resolution in pixels divided by the diagonal size in inches: diagonal_px = √(width² + height²), then PPI = diagonal_px ÷ diagonal_in. Fill in any three of width, height, diagonal, and PPI for a screen and the fourth is solved for automatically — useful when a spec sheet gives you PPI and diagonal but not the exact pixel count, or vice versa.
PPD (pixels per degree) additionally accounts for viewing distance — it's what actually determines whether individual pixels are visible to your eye, since a lower-PPI TV viewed from across a room can outresolve a higher-PPI phone held at arm's length. It's approximated with PPD ≈ PPI × distance × π ⁄ 180, matching the formula used by most "retina display" calculators.
Nothing you enter here is sent to a server — the entire tool runs as JavaScript in your browser tab.
Questions about PPI
What is PPI?
Pixels per inch: how densely packed a screen’s pixels are. Higher PPI looks sharper at the same distance.
What is the PPI of a 27-inch 1440p monitor?
About 109 PPI. A 27-inch 4K monitor is about 163 PPI.
What is a good PPI?
It depends on distance. Around 100–110 is fine for a desktop monitor, while phones held closer use 400 or more. Pixels per degree accounts for distance.
Is PPI the same as DPI?
They’re often used interchangeably, but DPI strictly means printer dots per inch; PPI is the right term for screens.