Online Ruler
Actual-size online ruler in cm, mm and inches
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0Launched Oct 2026
What is Online Ruler?
Online Ruler is a free set of measuring tools that run entirely in your browser. Its actual-size screen ruler shows centimeter, millimeter, and inch scales. Calibrate with a bank card or your screen diagonal so the ruler is true size on phones and high-DPI displays. Drag to read a distance, measure lengths and angles on a photo, and convert mm, cm, m, inches, feet, and pixels. No account; nothing is uploaded.
What it solves
- On-screen rulers are the wrong size on phones and high-DPI screens
- A physical ruler is not around when you need a quick measurement
- Photo lengths and unit conversions usually need another app
How it works
- Calibrate with a bank card or your screen diagonal
- Drag the cm, mm, and inch ruler to read a distance
- Measure a photo and convert mm, cm, inches, feet, and pixels
Key Features
online ruler
screen ruler
unit converter
image measure
Questions & Answers
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