Screen & image PPI calculator
Calculate pixel density (PPI) from a resolution and a diagonal size — for comparing monitors, laptops and phones, or checking an image shown at a given diagonal. PPI alone doesn't decide perceived sharpness; viewing distance matters as much.
Result
Pixel density
How to use this tool
- Enter the horizontal and vertical resolution in pixels.
- Enter the diagonal size in inches — the figure quoted as a screen's size.
- Read the pixel density. For a print measured by width rather than diagonal, use the DPI calculator instead.
Assumptions
- Treats the panel or image as a perfect rectangle with square pixels — true of essentially all modern screens.
- Uses the advertised diagonal; a panel's real viewable diagonal can be a fraction of an inch smaller.
Technical details: what the fields mean
- Horizontal resolution
widthPx - Horizontal resolution in pixels, e.g. 1920 for a 1080p screen or 2560 for 1440p.
- Vertical resolution
heightPx - Vertical resolution in pixels, e.g. 1080 or 1440.
- Screen diagonal
diagonalInches - Size measured diagonally, in inches — the number usually quoted in a spec sheet (e.g. '27-inch monitor').
Methodology
Diagonal resolution (px) = √(width² + height²). PPI = diagonal resolution ÷ diagonal size in inches, rounded to the nearest whole number.
Worked example
1920×1080, 24-inch monitor
Inputs: Horizontal resolution: 1920 px, Vertical resolution: 1080 px, Screen diagonal: 24 in
Result: 92 PPI
Choosing a 27-inch monitor: 1440p vs 4K
Inputs: Horizontal resolution: 2560 px, Vertical resolution: 1440 px, Screen diagonal: 27; then 3840×2160 at 27
Result: 109 PPI vs 163 PPI. At a typical desk distance both look sharp; 4K at 27 inches usually runs with 150% scaling, so text is crisper rather than smaller.
A 15.6-inch 1080p laptop
Inputs: Horizontal resolution: 1920 px, Vertical resolution: 1080 px, Screen diagonal: 15.6 in
Result: 141 PPI — the same pixels as the 24-inch monitor packed into a smaller screen, so noticeably denser.
A 3000×2000px image shown at a 20-inch diagonal
Inputs: Horizontal resolution: 3000 px, Vertical resolution: 2000 px, Screen diagonal: 20 in
Result: 180 PPI
Practical guidance
- Compare PPI together with viewing distance: a phone held at 30cm needs far more PPI to look sharp than a TV viewed from across the room.
- Higher PPI on a desktop monitor usually means using operating-system scaling; check that the apps you rely on scale cleanly.
- For prints, quality is usually judged by pixels per inch of print width — the DPI calculator gives that directly.
Common mistakes
- Comparing PPI across very different screen types (phone vs TV) without considering typical viewing distance.
- Using the diagonal method for a print size and comparing it with a 300 DPI print target, which is measured along the width.
FAQs
What is a 1920x1080 24-inch monitor's PPI?
About 92 PPI.
What PPI is a 27-inch 1440p monitor?
About 109 PPI; a 27-inch 4K monitor is about 163 PPI.
What PPI do I need for a sharp print?
200–300 PPI is a common target for prints viewed up close; posters viewed from a distance look sharp at much less. For prints, use the DPI calculator, which works from print width.
Last reviewed: 2026-10-11
A geometric calculation from resolution and size only — it doesn't account for viewing distance, subpixel layout or scaling, which all affect perceived sharpness.
This tool provides an indicative estimate, based on the assumptions stated above.
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