PPI Calculator - Pixels Per Inch & Dot Pitch

How to use this tool

Enter resolution. Type the horizontal and vertical pixel counts of your display.
Enter screen size. Type the physical diagonal size in inches or centimetres.
Read the results. PPI, dot pitch, total pixels, and aspect ratio are shown instantly.

What Is PPI?

PPI (pixels per inch) measures the pixel density of a screen: how many individual pixels are packed into each inch of display area. A higher PPI means sharper, crisper text and images because individual pixels become too small for the human eye to discern at normal viewing distances.

How PPI Is Calculated

First, the diagonal pixel count is derived using the Pythagorean theorem: diagonal_px = √(width² + height²). This is then divided by the physical diagonal size in inches: PPI = diagonal_px ÷ diagonal_in.

Retina Class Thresholds

Apple's "Retina" marketing threshold varies by device class and typical viewing distance. Phones (held ~12 inches away) need roughly 300+ PPI. Tablets (~18 inches) need ~220 PPI. Desktop monitors (~24 inches) need ~110 PPI to appear "pixel-perfect".

Dot Pitch

Dot pitch is the physical distance between adjacent pixel centres in millimetres. It is the inverse of PPI: dot_pitch_mm = 25.4 ÷ PPI. Smaller dot pitch = higher pixel density.

Common device PPI reference

Device	Resolution	Screen size	PPI
iPhone 16 Pro	2622 × 1206	6.3"	460 PPI
iPad Pro M4 (11")	2420 × 1668	11"	264 PPI
MacBook Pro 14" M3	3024 × 1964	14.2"	254 PPI
Dell UltraSharp 4K 27"	3840 × 2160	27"	163 PPI
Standard 1080p 27" monitor	1920 × 1080	27"	82 PPI

PPI and printing

Screen PPI and print DPI (dots per inch) are related but different. A display’s PPI describes pixel density; DPI describes how many ink dots a printer places per inch. For photographic print quality, 300 DPI is the standard. This means an image intended to print at 5 × 7 inches needs at least 1500 × 2100 pixels. Dividing your image’s pixel dimensions by the target DPI gives the maximum print size without visible loss of detail.

Frequently asked questions

What is PPI?

PPI (pixels per inch) measures the pixel density of a display - how many pixels fit into one inch of screen space. A higher PPI means sharper images and text.

What is "retina" display?

Apple coined "Retina" to describe displays where individual pixels are too small to distinguish at a normal viewing distance. Common thresholds are ~300 PPI for phones, ~220 PPI for tablets, and ~110 PPI for desktop monitors.

What is dot pitch?

Dot pitch is the physical distance between the centres of adjacent pixels, measured in millimetres. It is the inverse of PPI - a smaller dot pitch means higher density.

How is PPI calculated?

PPI = √(width² + height²) ÷ diagonal_inches. First compute the diagonal pixel count using the Pythagorean theorem, then divide by the physical diagonal size.