Measuring Angles using a Protractor

A protractor is a tool used to measure angles in degrees.

To read a protractor, align the baseline of the protractor with one side of the angle and look at the number where the other side of the angle crosses the scale.

A right angle measures 90 degrees.

An acute angle measures less than 90 degrees.

An obtuse angle measures more than 90 degrees but less than 180 degrees.

A straight angle measures exactly 180 degrees.

A full rotation is 360 degrees.

Place the protractor's center point at the vertex of the angle, align one side with the baseline, and read the measurement where the other side crosses the scale.

A 45-degree angle is an acute angle that is half of a right angle.

A 180-degree angle is a straight angle.