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How to use

Canonical: How to Use a Protractor →

Updated Online Protractor

Measure any angle in seconds — no install needed.

  1. Place the protractor’s center on the vertex.
  2. Align one arm to 0°.
  3. Drag the second arm to the other edge and read the angle.
  4. For photos: upload an image, then align the arms on top of it. Camera mode (where supported) follows the same steps.

Note: Perspective, lens distortion, screen scale, and finger placement affect results. See Accuracy & limitations.

Keyboard Shortcuts

  • R reset
  • L lock baseline
  • S cycle snap
  • I image
  • Z undo, Shift+Z redo
  • Arrow keys nudge 1° (Shift 5°)