Online Protractor

Using the online protractor is straightforward and works entirely in your browser without uploading any data to external servers.

1. Set Up Your Workspace

You can measure angles on a blank canvas or upload a background image (such as a photo of a physical object, a diagram, or a screenshot). If you upload an image, it will automatically scale to fit your screen, allowing you to measure angles directly on top of it.

2. Measure Using the Three-Point System

The fastest way to measure an angle is by clicking directly on the canvas:

1. Click once to place the Vertex (the point where the two lines meet).
2. Click a second time to place Arm A (the baseline of the angle).
3. Click a third time to place Arm B (the second line of the angle).

The tool will instantly calculate the interior angle in degrees and radians, classify it (e.g., acute, obtuse, reflex), and display the complement and supplement. You can drag any of the three points to adjust the measurement dynamically.

3. Use the Virtual Protractor Overlay

Alternatively, you can use the traditional protractor overlay:

• Drag the body of the protractor to position the center dot over your vertex.
• Drag the rotation handle to align the baseline with one side of the angle.
• Use the mouse wheel over the canvas for fine-tuned rotation (hold Shift for micro-adjustments).
• Toggle between 180° and 360° modes to measure straight, obtuse, and reflex angles.

4. Enable Snap and Grid

For precise measurements, enable the Snap feature to lock your angles to common increments (like 5°, 10°, or 15°). Toggle the background grid (square or dot) to help align your baseline with horizontal or vertical axes in your image.

5. Save and Export

Once you are satisfied with a measurement, click Save Measurement to add it to your history log. When you are finished, you can export all your recorded angles as a PNG image, or download the raw data as a CSV or JSON file for use in spreadsheets and reports.