Screen PPI calculator
Work out pixels per inch, dot pitch and aspect ratio from a screen’s resolution and diagonal size.
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Runs in this page in your browser; nothing is uploaded.
About this tool
Work out a screen’s pixel density from its resolution and diagonal size. Use it to compare monitors before you buy, for example a 27-inch 4K display with a 27-inch 1440p one, or to check the PPI of a phone or laptop screen you design for.
Enter the width and height in pixels and the diagonal in inches or centimetres, or start from a preset. The page shows pixels per inch, dot pitch in millimetres, the reduced aspect ratio, total pixels and the screen’s physical width and height. Everything is calculated in your browser and nothing is uploaded.
How to use it
- Enter “Width (px)” and “Height (px)”, 1920 × 1080 by default.
- Enter the “Diagonal” and choose the “Unit”: “Inches” or “Centimetres”.
- Or select a preset such as iPhone 16 Pro, MacBook Air or a 1080p, 1440p or 4K monitor.
- Read the PPI, “Dot pitch”, “Aspect ratio”, “Total pixels” and “Screen size”.
Common questions
How is PPI calculated?
PPI is the diagonal in pixels, √(width² + height²), divided by the diagonal in inches, so a 24-inch 1920 × 1080 screen comes to 91.79 PPI. Dot pitch is 25.4 mm divided by the PPI.
Can I enter the size in centimetres?
Yes. Choose “Centimetres” and the number is converted so the screen stays the same size. PPI is still given per inch, while the physical width and height are shown in centimetres.
Why is the aspect ratio shown as 64:27 instead of 21:9?
The ratio is the resolution reduced exactly, so 2560 × 1080 becomes 64:27 and 1366 × 768 becomes 683:384. The decimal next to it, such as 2.370, makes it easy to compare with rounded names like 21:9.
Can it detect my own screen?
No, it does not read your device. Enter the native resolution and the diagonal from the screen’s specifications; the 4K 32-inch preset, for example, uses a 31.5-inch diagonal.
How is the physical screen size worked out?
The width and height in pixels are each divided by the PPI, which assumes square pixels. A 24-inch 1920 × 1080 screen comes to about 20.92 × 11.77 inches.
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