Acute
More than 0° and less than 90°.
- 1Upload image
- 2Place 3 points
- 3Read the angle
- ✓ No installation
- ✓ Images stay on your device
- ✓ Works on desktop and mobile
Angle measurement workspace
Place points in orderA First sideB VertexC Second side
Drop an image hereor use the upload controls
Level
Snapped
Angle—
Five simple steps
How to Measure an Angle Online
- Upload or paste an imageChoose a JPEG, PNG or WebP file, drop it on the workspace, or paste a screenshot.
- Place the first pointPut point A on one side of the angle.
- Place the vertexPut point B exactly where the two sides meet.
- Place the final pointPut point C on the other side.
- Review and export the resultFine-tune coordinates, save measurements and export your work.
What Is an Online Protractor?
An online protractor is a browser tool for measuring or drawing angles on digital images. Unlike a physical protractor, it can zoom into a photograph, preserve multiple readings and create annotated exports. ProtractorLab performs the geometry locally, so your image stays on your device.
Measurement Modes
Use three-point mode for general image measurement, the vector protractor for a familiar scale, draw mode for exact diagrams, camera mode for captured scenes, or phone level for an approximate inclination reading.
Types of Angles
Right
Exactly 90°, within display tolerance.
Obtuse
More than 90° and less than 180°.
Straight
Exactly 180°, forming a line.
Reflex
More than 180° and less than 360°.
Full
Exactly 360°, one complete turn.
Practical Uses
Digital angle measurement is useful in geometry education, woodworking, roof and slope inspection, engineering drawings, architecture, photography, DIY projects, and posture or joint-angle observation.
Important: Image quality, lens distortion and point placement affect results. For medical, engineering, construction or other safety-critical decisions, verify measurements with suitable certified physical equipment and qualified professionals.
Accuracy Tips
- Use a sharp image taken straight-on to reduce perspective distortion.
- Zoom in and place the vertex precisely before adjusting the side points.
- Place side points farther from the vertex when the visible edges are long and clear.
- Use coordinate inputs and snapping for repeatable adjustment.
Image Privacy
Uploaded images and camera frames are decoded and measured inside your browser. They are not transmitted by this site. Workspace preferences may be stored in localStorage only when enabled; you can clear them from Advanced settings.