Use a protractor to measure the angle directly.
Place the protractor’s center point on the angle’s vertex.
Align one ray of the angle with the protractor’s zero line.
Read the degree mark where the other ray crosses the protractor.
Use angle relationships if the angle is part of a figure.
Add angles that form a straight line to get 180°.
Add angles around a point to get 360°.
Use complementary angles to get 90°.
Use supplementary angles to get 180°.
Use vertical angles, which are equal.
Use corresponding angles, which are equal when lines are parallel.
Use alternate interior angles, which are equal when lines are parallel.
Use triangle angle sum, which is 180°.
Use quadrilateral angle sum, which is 360°.
Solve for the unknown angle using algebra if an expression is given.