How Do You Read a Protractor?

read-protractor Credit: Johan/CC-BY-2.0

A protractor is an inexpensive math tool used to measure the sharpness of an angle in a geometric shape. Reading a protractor is fairly simple.

  1. Place the protractor on the angle

    The center point of the protractor is at the bottom in a circle. Place the point on the angle and line up the bottom line of the protractor with the straight edge that connects to the angle.

  2. Find the intersection

    Identify where the other side of the angle intersects with the protractor. Mark the line or make note of it.

  3. Read the angle

    Angles range from zero to 180 degrees. The protractor runs from zero to 90 and 90 to 180 on both sides to simplify measurement. If an angle is smaller than 90 degrees, the degree number is shown in the top left or lower right. For an angle over 90 degrees, the degree number is in the bottom left or upper right.