DPI / PPI calculator
Enter the pixel resolution and the diagonal in inches.
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Typical pixel densities
| Device class | Typical PPI | Why |
|---|---|---|
| Modern smartphone | 400–500 | Held 25–35 cm from the eye, so density has to be high |
| Tablet | 260–330 | Held slightly further away than a phone |
| Laptop (Retina / HiDPI) | 220–260 | Viewed at roughly 50 cm, with OS scaling applied |
| Standard 27″ 1440p monitor | ~109 | The classic desktop comfort zone at arm's length |
| 27″ 4K monitor | ~163 | Benefits from 150 % OS scaling |
| Print (standard) | 300 | Held in the hand — the long-standing print baseline |
| Large-format poster | 100–150 | Viewed from several metres |
Questions
What is the difference between DPI and PPI?
PPI (pixels per inch) describes a display; DPI (dots per inch) describes a printer. In everyday use the terms are swapped constantly and the arithmetic is identical, so the same calculator answers both.
How do I calculate PPI?
Take the diagonal in pixels — √(width² + height²) — and divide by the diagonal in inches. A 27-inch 2560 × 1440 monitor: √(2560² + 1440²) = 2937, divided by 27 = 109 PPI.
What is a good PPI for a monitor?
Around 110 PPI is the traditional desktop comfort zone. Anything above roughly 180 PPI benefits from OS scaling. Phones sit between 400 and 500 PPI because they are held much closer to the eye.
See also print sizes in pixels and device screen densities.