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Calculate PPI, pixel density, and aspect ratio for any screen resolution and size.
Screen resolution is the number of pixels displayed on a screen, expressed as width × height (e.g., 1920×1080), which determines image clarity and the amount of content visible.
| Name | Resolution | Ratio |
|---|---|---|
| HD (720p) | 1280×720 | 16:9 |
| Full HD | 1920×1080 | 16:9 |
| QHD (1440p) | 2560×1440 | 16:9 |
| 4K UHD | 3840×2160 | 16:9 |
| Ultrawide | 3440×1440 | 21:9 |
| 8K UHD | 7680×4320 | 16:9 |
PPI = √(W² + H²) ÷ DiagonalPitch = 25.4 ÷ PPIFormula
PPI = √(W² + H²) ÷ Diagonal | Pixel Pitch (mm) = 25.4 ÷ PPI | Total Pixels = W × HW, H = screen width and height in pixels
Diagonal = physical screen diagonal size in inches
PPI = pixels per inch — the pixel density of the display
25.4 = millimeters per inch — converts PPI to physical pixel pitch
Worked Example
1920×1080 display on a 24-inch monitor
Did you know? Apple's 'Retina' branding has no fixed PPI threshold — it varies by device. The iPhone Retina threshold is ~300 PPI (held at arm's length), while the MacBook Pro Retina threshold is ~220 PPI (held further away). The key criterion is that pixels become indistinguishable at typical viewing distance.
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