How to Use a Protractor

Try it live

Follow the steps below and practice directly. Leave it on “Snap: 5°” while learning — turn off snap for fine readings.

Step-by-step

1. 1
   Place the center on the vertex

   Drag the glowing ring to the corner where the two edges meet. Turn on crosshair and grid in More for alignment; a magnifier appears near the active handle while dragging.
2. 2
   Align the baseline to 0°

   Drag handle A so the first ray sits exactly on one edge of the angle. The baseline value is always 0° — the reading is the rotation from A to B. Use Lock baseline to keep A fixed while you move B.

   Tip: start with baseline horizontal — it matches how most textbooks draw protractors.

3. 3
   Drag the second ray and read

   Drag handle B to the second edge. The chip shows the inner angle (≤180°) and, in smaller text, the reflex complement (360°−inner). Press Copy — it copies degrees or radians depending on the toolbar toggle.

   Snap: 5° by default. Use 1° for fine work, 15°/45°/90° to land on common angles.

   Reflex: toggle “Measure reflex angle” to make the larger side primary.

Photos, keyboard, and radians

Accuracy note: perspective, lens distortion, screen scale, finger placement and camera limits affect what you measure — for construction or safety work, verify with a calibrated physical protractor. Read accuracy →

Common follow-ups