How To Use A Protractor 8 Steps With Pictures

At a glance, we can tell this angle is acute because it is less than 90 degrees.

The baseline is parallel to the edge, but is not the flat edge of the protractor. It is aligned with the center of the origin and the line projects to the start of the scale on either side.

In the above example, the angle measure is 30 degrees. We know to use the smaller scale because we determined that our angle was less than 90 degrees in the first step. If the angle was obtuse, we would use the scale that indicated an angle larger than 90 degrees. Initially, the measurement scale may seem confusing. Most protractors have two opposing ruler grids, one on the inner side of the arc and one on the outer. This makes the tool handy for measuring angles originating from either direction.

You can use the flat edge of your protractor to draw this line. The length of the line doesn’t matter.

You don’t have to place the point at the edge of the line. It can be placed anywhere on the line, but is easier just to use the end of the line.

Remember, the baseline is parallel to the edge, but is not the flat edge of the protractor. It is aligned with the center of the origin and the line projects to the start of the scale on either side. In the above example, the angle is 40 degrees.