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📏 Online Ruler

Actual size screen ruler for measuring objects

Calibrate

💡 Usage Tip Place the object on the screen and align it with the ruler markings. Please calibrate your screen before first use.
📏
Length Converter
Convert length units instantly between metric and imperial systems
📐
Area Converter
Convert area units instantly, metric, imperial and land units
Rate:
💬 Comments: 3
Z
Zoe

Works on any screen.

2026-01-12
H
Hannah

Accurate screen ruler!

2026-01-11
T
Tyler

Very useful tool.

2025-12-19

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

📏 Actual Size

Shows real dimensions after calibration

🔧 Easy Calibration

Quick calibration with card or coin

📐 Dual Units

Switch between cm and inches

💾 Save Settings

Auto-saves calibration value

📱 Responsive

Works on various screen sizes

🎯 Precise Marks

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.

Last Updated: 2026-06-04✓ Expert Verified