Our Purpose
Standard screen rulers default to 96 PPI, causing major errors on modern retina and mobile screens. Online Ruler provides exact 1:1 physical measurements directly in your web browser without installing apps.
Calibration Technology
We calculate exact pixel density using CSS pixel normalization, Device Pixel Ratio (DPR), screen diagonal geometry, and physical credit card matching.
Privacy & Accessibility
100% client-side and free. No camera access required, no trackers, and no measurement logs stored on any server.