Compute pixel density (PPI), dot pitch, and the minimum viewing distance at which the human eye stops resolving individual pixels. Useful for picking a monitor, sizing a UI element on a phone, or deciding whether @2x assets are worth shipping.
A pixel becomes individually invisible when it subtends less than 1 arcminute on the retina (the threshold of 20/20 vision). Below this distance, you can technically resolve the pixel grid; above it, the display looks perfectly smooth.
| Distance metric | Inches | Centimeters | Notes |
|---|
In-browser detection. The browser only knows CSS pixels and the device pixel ratio (DPR); the physical PPI requires a known screen size, which the browser can't measure.
Pick a device to autofill the resolution and diagonal.
| PPI band | Examples | What it means |
|---|---|---|
| 72–96 | Older monitors, projectors, TVs at couch distance | Pixel grid visible up close; "1× assets" target. |
| 96–150 | 1080p/1440p desktop monitors | The historical baseline for Windows / web design. |
| 150–220 | 4K 27" / Apple "Retina" desktops, tablets | Smooth at arm's length; benefits from 2× assets. |
| 220–400 | Laptops (MacBook), high-end tablets | Pixel grid invisible at normal use distance. |
| 400–600+ | Modern smartphones | Effectively impossible to resolve individual pixels. |