How to Use a Protractor

A protractor is a tool that allows you to measure an angle or construct an angle of a given measure.

Instructions

To Measure an Angle

1

Find the center hole on the straight edge of the protractor.

2

Place the hole over the vertex, or point, of the angle you wish to measure.

3

Line up the zero on the straight edge of the protractor with one of the sides of the angle.

4

Find the point where the second side of the angle intersects the curved edge of the protractor.

5

Read the number that is written on the protractor at the point of intersection. This is the measure of the angle in degrees.

To Construct an Angle

6

Use the straight edge of the protractor to draw a straight line. This line will form one side of your angle.

7

Find the center hole on the straight edge of the protractor.

8

Place the hole over one end point of the line you have drawn.

9

Line up the zero on the straight edge of the protractor with the line.

10

Make a mark at the number on the curved edge of the protractor that corresponds to the desired measure of your angle. For example, mark at 90 for a 90-degree angle.

11

Use the straight edge of the protractor to connect the mark to the end point of the first line, forming an angle.