How it works
Measure an angle with three points
- Work on the blank canvas or upload an image. The image is scaled to fit the canvas; drag it to reposition it behind your measurements.
- Click the angle's vertex, then click a point along the first arm and a point along the second arm.
- Read the result in degrees or radians. The tool also classifies the angle and shows its complement and supplement.
- Drag the vertex or either arm point to refine the measurement. Select Clear Points or press Esc to start again.
The three-point method returns the smaller angle by default. To measure the larger, reflex angle, select 360° and enable Reflex angle before placing or adjusting the points.
Use the virtual protractor
You can also read an angle with the protractor graphic on the canvas. Drag its body to move it, then drag the rotation handle to align it with one side of the angle. With snapping off, scroll over the canvas to rotate in 1° steps; hold Shift for 0.1° adjustments. Choose the 180° or 360° range to match the angle you are measuring.
Snap, save, and export
Set Snap to Common angles to round to 15° increments, or choose Step and enter a value from 1° to 90°. Leave snapping Off for an unsnapped reading. Snapping affects the displayed measurement, so turn it off when you need the angle calculated directly from your point placement.
Select Save Measurement to add the current three-point reading to the list. Export the canvas as a PNG or download saved measurements as CSV or JSON. All image handling and angle calculations happen in your browser; the tool does not upload your image.
When measuring from a photograph, align the points with the two straight edges that form the angle. Camera perspective can distort angles in a photo, so a straight-on view is best for a flat diagram or surface.