PPI Calculator
Calculate your screen's pixel density from its resolution and physical diagonal size. Width and height are auto-filled from your device — enter the diagonal in inches and press Calculate.
Results
Enter your screen details and press Calculate to see PPI, dot pitch, display size, and more.
Frequently asked questions
What is PPI and why does it matter?+
PPI (pixels per inch) describes how many pixels your display packs into one inch. The ruler converts pixels to centimeters and inches using your PPI, so getting it right is what makes measurements accurate.
How do I find my screen's diagonal size?+
It's the manufacturer's advertised size — the distance corner to corner across the display, in inches (for example, a 27-inch monitor or a 13.3-inch laptop). Check the spec sheet or product listing if you're unsure.
What is dot pitch?+
Dot pitch is the physical distance between pixels, here shown in millimeters. A smaller dot pitch means a sharper, denser display.
Can I use the calculated PPI in the ruler?+
Yes. After calculating, press "Use this PPI for ruler" to save it and open the online ruler already calibrated to your screen.