Screen DPI Calculator

Calculate a screen's pixel density (PPI) from its resolution and diagonal size in inches — useful for comparing display sharpness across devices.

How PPI is calculated

1. Find the diagonal resolution with the Pythagorean theorem: √(width² + height²).
2. Divide it by the diagonal screen size in inches.

Example: a 24-inch 1920 × 1080 monitor has √(1920² + 1080²) ≈ 2,203 pixels across the diagonal, and 2,203 ÷ 24 ≈ 92 PPI.

Typical pixel densities

Screen	Resolution	PPI
24-inch Full HD monitor	1920 × 1080	about 92
27-inch QHD monitor	2560 × 1440	about 109
27-inch 4K monitor	3840 × 2160	about 163
6.1-inch modern smartphone	2556 × 1179	about 461

How much PPI do you need?

It depends on how far away you sit. Phones are held about 10–12 inches from your eyes, so they need 400+ PPI to look perfectly sharp. A desktop monitor at arm's length looks sharp at around 110–160 PPI, and a TV across the room looks fine at much lower densities. That's why a 65-inch 4K TV, at only about 68 PPI, still looks crisp from the couch.

PPI vs. DPI

PPI (pixels per inch) describes screens and digital images. DPI (dots per inch) originally describes printers — how many ink dots they place per inch. The terms are often mixed up. For printing photos, 300 pixels per inch of print size is the usual target for sharp results: a 4 × 6 inch print needs about 1200 × 1800 pixels.

Frequently asked questions

What is PPI?

Pixels per inch — how densely packed the pixels are on a screen. Higher PPI generally means sharper, crisper detail at a normal viewing distance.

How is it calculated?

PPI = diagonal resolution in pixels ÷ diagonal screen size in inches, where the diagonal resolution is found using the Pythagorean theorem on the horizontal and vertical pixel counts.

Is higher PPI always better?

Only up to the point where your eyes can't see individual pixels at your viewing distance. Beyond that, extra pixels add cost and use more battery or graphics power without a visible benefit.