How to Use a Protractor: Lesson for Kids

Instructor: Mark Boster
This lesson will teach you what a protractor is and how to use one. It will show you how to line a protractor up correctly, read the measurements, and determine which measurement is correct.

What Is a Protractor?

Meet Hank the dog. Hank is measuring his dog house so that he can build one exactly the same for his friend, Doug. He uses a yardstick to take the measurements: His house is 48 inches deep and 24 inches wide, and the walls are 36 inches tall. But there's a problem. Hank needs to find a way to measure the angle on the top of his house and the angle of the ramp. Then, he will be able to make the tip of the roof and the ramp the same angle on Doug's house.

Hank in his house
Hanks house

How can he measure those angles? Hank can use a protractor, which is a tool used to measure the number of degrees (sometimes represented as °) in an angle. The higher the degree, the more open the angle is.

This is a protractor.

This protractor is divided into 180 degrees.

Using a Protractor

To measure an angle, start by placing the dot in the center line (the zero line) directly on the point of the angle's corner so that one edge of the angle sits on the center line. Then, find where to other line of the angle falls. This spot on the protractor will tell you the number of degrees of the angle.

As you may have noticed, protractors display two numbers at each line--one number for the measurement from each corner of the protractor. That's so you can start measuring the angle from either corner of the protractor. Just make sure, when measuring, to start at zero line and follow numbers upward on the curve along the protractor until you reach the other edge of the angle.

Let's try it with the roof on Hank's dog house:

The dot gets placed on the corner of the angle, with one side of the dog house sitting on the center line.

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