Features
Everything you need for precise angle measurement
This online protractor provides professional-grade angle measurement tools in your browser. Upload images, draw rays to find angles, and export your work—all without installing software. Our online protractor runs locally on your device for complete privacy.
Ray-Based Angle Measurement
Click to place rays from the protractor center for precise angle measurement. Angles between adjacent rays are calculated automatically and displayed in real-time. Switch between degrees (0-360°) and radians. Adjust decimal precision from 0 to 4 places for measurements like 45.0000°. Toggle between inner and outer angles. Drag ray endpoints to adjust—you'll see a live preview as you move. Each ray can have a custom color for better visibility against your background images.
Image Upload & Overlay
Upload PNG, JPG, or other image formats to measure angles on photos, diagrams, or technical drawings using this online protractor. Images appear at the canvas center, automatically scaled to fit 60% of your viewport. Drag images to reposition them. Use corner handles to resize, and the rotation handle (top-center) to rotate. Adjust opacity from 0% to 100% to balance visibility between your image and measurement overlays. Lock images to prevent accidental changes while you work.
Multiple Protractors
Add as many protractors as you need to your workspace. Each protractor operates independently—move, rotate, and scale them separately. Click the '+' button to add a new protractor, or duplicate an existing one to copy its color and settings. Choose between semicircle (180°) and full circle (360°) styles. Lock protractors to prevent accidental movement while you measure angles.
Flexible Export Options
Export measurements as CSV files with columns for protractor ID, ray ID, angle, length, and color. Save your entire workspace as JSON to reload later—includes all protractors, rays, images, and settings. Export the canvas as PNG or JPEG at 1x, 2x, or 4x resolution for high-quality prints. Choose transparent, white, or black backgrounds. Optionally export only the measurement overlay without background images.
Undo & Redo
Full undo and redo support for all operations: creating, moving, rotating, scaling, and deleting protractors and rays. History stack maintains up to 50 steps. Use keyboard shortcuts Cmd/Ctrl+Z to undo and Cmd/Ctrl+Shift+Z to redo. Press Delete or Backspace to remove selected objects. Never lose work due to accidental changes.
Grid & Ruler Overlays
Enable grid overlay for visual alignment guides with customizable spacing (10px to 100px) and opacity. Toggle ruler overlay to measure distances in pixels. Grid and ruler help you position protractors and align measurements precisely. Both overlays can be toggled on or off independently to suit your workflow.
Angle Snapping
Enable angle snapping to lock rays to whole degrees or custom increments (1°, 5°, 10°, 15°, 30°, 45°, or 90°). When you drag a ray near a snap point, you'll see a visual hint. Snapping helps you create consistent measurements and align rays to specific values. Disable snapping when you need freeform precision.
Keyboard Shortcuts
Press V to activate the Select tool, M for Measure Angle tool, or Space for Pan View tool. Use Cmd/Ctrl+Z to undo and Cmd/Ctrl+Shift+Z to redo. Press Delete or Backspace to remove selected objects. These shortcuts speed up your angle measurement workflow significantly when making many measurements with the online protractor.
View Controls
Zoom in and out using the zoom buttons in the toolbar. Pan the canvas by holding Space and dragging, or switch to Pan View mode. Reset the view to default position and zoom with one click. The current zoom level is displayed as a percentage. All view changes are smooth and responsive.
Customizable Display
Change protractor tick mark colors to create contrast against your background images. Adjust protractor scale from 0.1x to 5x for precise alignment. Rotate protractors from 0° to 360° to match any orientation. Set ray colors individually for better visibility. The protractor uses a glass-like appearance that adapts to light and dark themes automatically.
Lock Objects
Lock protractors, rays, or images to prevent accidental changes. Locked objects cannot be moved, rotated, scaled, or deleted until you unlock them. This is useful when you have a complex setup and want to protect certain elements while adjusting others. Lock status is indicated by a yellow highlight.
Private & Secure
Your data never leaves your device. All measurements and images are processed locally in your browser using client-side JavaScript. No account required, no data collection, no tracking. Export your work to save it locally. Your privacy is guaranteed because we never see your data.
Ready to Start Measuring?
Try all these features now with our free online protractor. No installation or account required.