Miscellaneous
PPI Calculator - Pixels Per Inch & Dot Pitch
Calculate pixels per inch (PPI), dot pitch, and total pixel count from your screen resolution and diagonal size. See whether your display is retina-class.
Pixel density scale
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.