zztool What is an Online Ruler?
An online ruler is a tool that displays actual size markings on your screen. By calibrating your screen's PPI (pixels per inch), the ruler can show accurate centimeter or inch scales for measuring small objects.
Features
Shows real dimensions after calibration
Quick calibration with card or coin
Switch between cm and inches
Auto-saves calibration value
Works on various screen sizes
Millimeter-level accuracy
FAQ
Why do I need to calibrate?
Different screens have different pixel densities (PPI). Calibration ensures the ruler displays correct actual sizes.
Will calibration be saved?
Yes, the calibration value is stored in your browser and will be loaded automatically on your next visit.
How large objects can I measure?
It depends on your screen size. Generally, you can measure objects up to 15-30 cm.
Can I use it on mobile?
Yes, but a larger screen is recommended for better measurement experience.
Works on any screen.
Accurate screen ruler!
Very useful tool.