When you need this calculator
Choosing between monitors, checking whether a screen will need display scaling, comparing a laptop’s panel to a desktop’s, or working out how large a design will appear on a specific device. Resolution alone doesn’t tell you sharpness. The same 1920 × 1080 pixels look crisp on a 13-inch laptop and coarse on a 32-inch monitor.
How it’s calculated
The screen’s diagonal in pixels comes from Pythagoras: √(width² + height²). Dividing by the physical diagonal in inches gives pixels per inch. Physical width and height follow by dividing each resolution by the PPI.
PPI and display scaling
Operating systems target a comfortable size for text and controls. On a high-PPI display they draw everything larger (125%, 150%, 200%) so a button stays the same physical size but with more detail. As a rough guide at desk distance:
- Under ~100 PPI: text looks slightly soft; 100% scaling.
- ~110–140 PPI: sharp at 100%, or 125% for comfort.
- ~160 PPI and up: usually 150–200% scaling (“Retina”-style).
Common mistakes
Comparing PPI across device types. A phone is held at 30 cm, a monitor at 60 cm, a TV at 2–3 m. A lower PPI at a greater distance can look just as sharp.
Using CSS pixels. Enter the panel’s native resolution, not the scaled resolution the operating system reports.