A proportional shape comparison diagram compares two (or more) values by using the area of shapes, usually squares, rectangles, or circles. They are popular because they instantly communicate the difference in the values to a viewer. We see more and more of these diagrams used in newspapers and magazines. Here is an example of one I used recently for a client.
You can easily see how much smaller the number of e-mails is compared to voice calls and this representation is more effective than a pie chart or column chart would be in this case. You can also use this type of diagram to compare multiple values that are related. Here is an example from a recent presentation.
It is important that the shapes be exact to the proportions of the numbers being compared, or else the audience is being misled. In order to make the calculations easier, I have created an online tool below that will do all the necessary calculations for you if you have two shapes (if you want to compare up to 10 shapes, use my updated Proportional Object Collection Calculator). Here is how you use the calculator below.
- In the form below at the top, enter the large value and the small value you want to represent in the diagram.
- The second section defines the size of the large shape. I have chosen default values for these shapes based on what will fit on most corporate templates. I suggest you only change these values if you have a particular need to make the shapes smaller or bigger to fit the area of the slide that you have.
- The next three sections give you the dimensions for the large and small shapes to create three different types of proportional shape comparison diagrams. The third section gives you dimensions for side-by-side squares (like the first example above). The fourth section gives you dimensions for overlapping rectangles (like the second example above). The fifth section gives you dimensions for circles that can be side-by-side or overlapping.
- Using the dimensions from the tool, enter the height and width of the shape in PowerPoint. You can enter the exact height and width in the Size section of the Drawing Tools ribbon in PowerPoint. Notice that the dimensions given are in centimetres (cm). Just enter the dimensions exactly as shown, i.e. 10cm, and PowerPoint will convert it to the default units you use. Remember to enter both height and width dimensions. Here is an example of the dimension being entered.
- Set the shapes to whatever fill colors you want. I suggest you have no outline to the shapes as the outline adds a slight amount to the area and it makes the comparison slightly off. It also looks cleaner without an outline.
- Move the shapes to where you want them to be on the slide. I suggest that you use the Align feature to line up the bottom of the shapes. If you are using overlapping rectangles, you will also want to Align the left or right edges of the shapes. If you are using overlapping circles, I suggest Aligning the shapes in the middle.
- Add text inside or outside the shapes to indicate what each shape represents. It may also be a good idea to add the value to the description for those who want to know the number being represented by the shape.
Once you use the tool a few times and see how easy it is to create this type of comparison diagram, you will be able to replace some of the pie charts, column charts, or other diagram you have been drawing by hand to approximate comparisons.