What is an Obtuse Angle?
An angle whose measure is greater than 90° and less than 180°
An obtuse angle is an angle that is larger than a right angle. In math, angles are measured in degrees. A right angle is exactly 90°, so an obtuse angle is any angle that measures more than 90° but less than 180°.
For example:
- A 120° angle is obtuse.
- A 95° angle is also obtuse.
Obtuse angles appear in real life wherever things open larger than a right angle, like the flaps of an open book or the hands of a clock at 10:10.
Understanding angle types—acute, right, obtuse, and straight—helps students explore shapes, geometry, and how things turn or rotate.
When Do Students Learn About Obtuse Angles?
Students begin learning about obtuse angles as they explore basic geometry and measure angles with protractors.
Grades 3–5 – Introduction to Obtuse Angles
Students learn to recognize and measure different types of angles, including obtuse, using hands-on tools and visuals.
Grades 6+ – Applying Angle Concepts in Geometry
Students use obtuse angles in more complex geometric problems, coordinate plane work, and reasoning tasks.
