Types of Angle

In a Nutshell

Angles are classified by size: acute (less than 90°90°), right (exactly 90°90°), obtuse (between 90°90° and 180°180°), straight (180°180°), and reflex (between 180°180° and 360°360°).

Every angle falls into one of five categories based on its size:

  • Acute angle: greater than 0°0° and less than 90°90°.
  • Right angle: exactly 90°90°. Marked with a small square.
  • Obtuse angle: greater than 90°90° and less than 180°180°.
  • Straight angle: exactly 180°180°. The two arms form a straight line.
  • Reflex angle: greater than 180°180° and less than 360°360°.

Being able to classify angles quickly helps you estimate and check measurements. If you measure an angle as 130°130°, you should expect it to look wider than a right angle but not as wide as a straight line.

Angle classifier showing types of angle An interactive diagram showing five types of angle: acute, right angle, obtuse, straight, and reflex, with their defining ranges in degrees. Acute 0° < angle < 90° 45°

Press each button to see the angle type, its range and how the arms are positioned.

Watch it work

Question: Classify each angle: 72°72°, 180°180°, 95°95°, 210°210°.

Have a go

Q1. Classify an angle of 89°89°.

Q2. Classify an angle of 162°162°.

Q3. An angle is described as reflex. Give a possible value for the angle.

Q4. True or false: a right angle is a special case of an obtuse angle.

Q5. The minute hand of a clock moves from 12 to 3. What type of angle has it turned through?