This online ruler works on any desktop or mobile screen. It automatically detects your device and scales the on‑screen ruler to real size. With full‑screen and calibration options, your tablet, phone, or computer becomes a true measuring tool no installation required.
help How to Use the Online Ruler
The ruler usually auto‑detects your device and displays accurate cm / inch scales. If detection fails, enter your screen size once or calibrate for pixel‑perfect dimensions.
1. 📱 Automatic Device Detection
Works out of the box—no setup.
Recognizes 100 + Apple, Samsung, Google, and other devices.
Applies the correct factory PPI.
A green “Detected” box confirms accuracy.
Settings persist between visits.
2. 💻 Set Your Screen's Diagonal
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