How to read the protractor

Start from the baseline at 0circ0^circ, then read counterclockwise until you reach the active ray.

The same degree measure can also be interpreted as a fraction of a full turn, which is useful in rotation problems and circular motion.

The side panel keeps the supplementary and complementary checks nearby so you can classify the angle quickly.

Quick angle facts

  • Acute angles are less than 90circ90^circ.
  • Obtuse angles are between 90circ90^circ and 180circ180^circ.
  • Reflex angles are greater than 180circ180^circ and less than a full turn.