What This Tool Does
Protractor Online provides an interactive semicircular protractor you can move, rotate, resize, and place over an uploaded JPG, PNG, or WebP image.
It is designed for visual angle alignment and reading degree markings—not for automatic corner detection.
Core Features
Upload a local image, adjust protractor color for contrast, change radius and zoom, set position and rotation, and export the canvas as PNG.
Images are processed in your browser; we do not upload your files to a server for measurement.
- Drag or use numeric controls to position the protractor
- Dual 0°–180° scales on the semicircle
- Download PNG snapshots for notes or sharing
- Works on desktop and supported mobile browsers
Who It Is For
Students checking geometry homework, teachers demonstrating how to read a protractor, and anyone estimating angles in diagrams, screenshots, or photos.
Results depend on alignment and image quality; the tool is not a substitute for certified measuring instruments in engineering or construction.