Circle graphs, also known as pie charts, are the best type of graph for showing the relative proportions of different categories to each other and to the whole.

Circle graphs are used when exact quantities are less important than the relative sizes of the parts:

Source: U.S. Bureau of the Census, Projections of the
Population of the United States by Age, Sex, and Race, 1995-2050 (1996).

The title explains the topic or subject of the whole the --100%--that the chart represents.
What is the title of the graph above? Ans.

The key or legend indicates the categories included and which pattern or color represents each category.
What age range does the color purple represent? Ans.

Rather than provide a key or legend, some circle graphs directly label each part:

Source: Peter Drukmeir, Earth Day 1990 Water Conservation Fact Sheet

Circle graphs usually indicate the percentages of the various categories that are being graphed:

Source: U.S. Department of Education

What was the largest type of degree awarded in the academic year 1996-97? Ans.

Sometimes circle graphs give the actual quantities for each category:

Source: Office of Institutional Research, Academic Affairs. BMCC Fact Book, 1998-1999

The footnote or source tells where the information comes from. Looking at the source of the graph above,
should you trust the information presented?Ans.

The main points or ideas of a pie chart come from a combination of the topic and the information represented.
What is the main idea of this chart?Ans.

Often pairs or groups of circle graphs are used to convey a great amount of information quickly:

How the Federal Government Spent your Tax Dollar

Source: Tax Foundation, OMB

Comparing the data from 1962 and 1992:

What category of spending has had the largest increase?Ans.

What is significant about the federal government’s spending on national defense? Ans.

For practice on circle graphs exercises, click on the arrow below

To go on to bar graphs, Click here

To go on to line graphs, Click here