Screen Ruler
A calibrated on-screen ruler. Enter your display diagonal to compute PPI and show real-world measurements in centimeters or inches.
Enter your screen diagonal to display the ruler.
How the ruler is calibrated
Enter your screen's diagonal size in inches. The tool computes your PPI using your detected screen resolution and device pixel ratio, then converts pixels to real-world centimeters and inches. The rulers ticks are spaced exactly 1 unit apart.
Accuracy note
Browser-reported screen dimensions may differ from physical display size on high-DPI screens with fractional scaling. For best accuracy, use the logical resolution (the default Windows display resolution setting, not the physical pixel count) with your known physical diagonal.
Also see our Pixel Density Calculator for full PPI and dot-pitch computation.