# Online Ruler
> Free Online Ruler - Pixel-perfect screen measurement in cm, mm, inches & pixels
> https://ruler.kiveo.org

Online Ruler is a free browser-based measuring tool. Calibrate your screen once with smart auto-detect, screen diagonal, or credit card calibration, then measure anything on screen with edge rulers, click-to-measure, and live cursor coordinates. No installation, no account, no limits.

## Pages

- [Online Ruler Tool (English)](https://ruler.kiveo.org/en) : Main tool with 4 units, multi-edge rulers, click-to-measure, and 3 calibration methods
- [在线尺子（中文）](https://ruler.kiveo.org/zh) : 主工具，支持 4 种单位、多边缘尺子、点击测量与 3 种校准方式
- [Contact](https://ruler.kiveo.org/en/contact) : Reach the Online Ruler team or send feedback
- [Privacy Policy](https://ruler.kiveo.org/en/privacy) : Calibration and preference data stays in your browser localStorage
- [Terms of Service](https://ruler.kiveo.org/en/terms) : Usage terms and accuracy disclaimer

## Keyword Guides

- [Ruler in CM — Online Ruler Measured in Centimeters](https://ruler.kiveo.org/en/ruler-in-cm) : Use this ruler in cm to measure objects on your screen in centimeters. Free online ruler with millimeter marks, instant calibration, and pixel-perfect accuracy.
- [厘米尺子 — 屏幕上直接量厘米的在线尺子](https://ruler.kiveo.org/zh/ruler-in-cm) : 用这款厘米尺子在屏幕上按厘米测量物体。免费在线尺子，带毫米刻度，校准一次即像素级精准。
- [Ruler in Inches — Online Ruler Measured in Inches](https://ruler.kiveo.org/en/ruler-in-inches) : Free ruler in inches for your screen. Calibrate once and measure in inches and fractions with a pixel-perfect online ruler. No install, no limits.
- [英寸尺子 — 屏幕上直接量英寸的在线尺子](https://ruler.kiveo.org/zh/ruler-in-inches) : 免费的英寸尺子，校准一次即可在屏幕上按英寸和分数刻度测量。像素级精准的在线尺子，无需安装。
- [Pixel Ruler — Measure Your Screen in Pixels](https://ruler.kiveo.org/en/pixel-ruler) : Free pixel ruler for designers and developers. Measure any distance on screen in px with this online ruler, plus cm, mm, and inches after calibration.
- [像素尺子 — 按像素测量屏幕](https://ruler.kiveo.org/zh/pixel-ruler) : 免费像素尺子，设计师和开发者用它在屏幕上按像素测量距离，校准后同样支持厘米、毫米和英寸。

## Features

- Smart Auto-Detect: 100+ device PPI profiles matched by resolution, pixel ratio, and user agent
- 3 Calibration Methods: auto-detect, screen diagonal, credit card (ISO 85.6mm × 54mm)
- 4 Units: centimeters, millimeters, inches, pixels
- Multi-Edge Rulers: top, bottom, left, right, or any combination
- Click-to-Measure: horizontal, vertical, and diagonal distances between any two points
- Live Cursor Position: real-time X/Y coordinates in px and calibrated units
- Dark Mode: follows your system preference, toggle anytime
- Keyboard shortcuts: U (unit), M (measure), E (edges), Esc (exit)
- Multi-Language: English, Chinese
- 100% Free, no sign-up required