About Us
Welcome to Online-Ruler.Onl, a free screen-based measurement utility for situations where a physical ruler is not available.
A browser cannot determine a display's physical size reliably on its own. The tool therefore starts uncalibrated and asks you to match a standard card or enter a manufacturer-listed screen diagonal before measuring.
Our Mission
To provide an accessible and transparent online measurement aid with clear calibration steps and limitations.
Our Vision
To be the most trusted and widely used digital measurement tool in the world, helping millions of people in their daily measurement needs.
Why Choose Online-Ruler.Onl?
Explicit Calibration
The ruler identifies uncalibrated output and requires a physical reference or known display diagonal before showing a calibrated state.
100% Free
No sign-ups, no subscriptions, no hidden costs. Always free.
Easy to Use
Intuitive interface designed so anyone can use it without complications.
Designed for Modern Screens
Designed for modern computers, tablets, and smartphones. Results vary with browser zoom, display scaling, and device geometry.
Transparent Data Use
Calibration stays in page memory and resets on reload. Google Analytics and AdSense are disclosed in our Privacy Policy.
How We Review Measurement Content
Articles are maintained by the Online Ruler Editorial Team. For standards and unit definitions, we prioritize primary references from organizations such as the Bureau International des Poids et Mesures (BIPM) and the U.S. National Institute of Standards and Technology (NIST). Product pages state known limitations instead of promising universal accuracy.
Corrections and device-test feedback can be sent through our Contact page. For critical measurements, use an appropriate certified physical instrument.