About Online Ruler
How the screen ruler works, and what affects accuracy
Online Ruler is a browser-based screen ruler. You can measure in pixels (px) and, after PPI calibration, estimate centimeters or inches at a closer 1:1 scale. Guides and the Selection tool help align and read sizes, but results still depend on zoom, display scaling, and hardware.
Purpose
Make on-screen measuring straightforward: show reliable px sizes, and provide calibration to approximate real-world units with clear limitations.
Principles
Prefer clarity over claims. Explain what calibration changes, keep the interface simple, and keep settings on your device.
Team
Built and maintained by developers who use it for UI layout checks, print-on-screen references, and quick px measurements.
Technology
Built with Next.js, React, Tailwind CSS, and next-intl. The ruler runs in the browser; calibration and preferences are stored locally.