A pie chart is a circular chart divided into wedge-like sectors, illustrating proportion. Each wedge represents a proportionate part of the whole, and the total value of the pie is always 100 percent.
Pie charts can make the size of portions easy to understand at a glance. They're widely used in business presentations and education to show the proportions among a large variety of categories including expenses, segments of a population, or answers to a survey.
Should You Use a Pie Chart or a Bar Chart?
Some critics of pie charts point out that the portions are hard to compare across other pie charts and if a pie chart has too many wedges, even wedges in a single pie chart are hard to visually contrast against each other compared to the height of bars in a bar graph for example.
Bar charts are easier to read when you're comparing categories or looking at change over time. The only thing bar charts lack is the whole-part relationship that makes pie charts unique. Pie charts imply that if one wedge gets bigger, the other has to be smaller. This would not be true of two bars on a bar chart.
Tips for Creating Better Pie Charts
Don't use more than 5 slices in any pie chart otherwise it becomes too hard to read.
Don't use a pie chart if the values of the wedges are close to each other and it's important to see the differences. For example, 32%, 33% and 35% will look pretty even at a glance when illustrated on a pie chart. Using a bar chart will make the differences more obvious.
Don't use a pie chart if what you're comparing are not parts of a whole. For example, it makes sense to use a pie chart to compare the profitability of different divisions inside a larger enterprise. However, it doesn't make sense to compare different companies using a pie chart since there's a much larger number of companies and they don't belong to any meaningful whole.
Categories on the pie chart must be mutually exclusive and not overlapping.
History of Pie Charts
Pie charts have been around since the 1800s when they were used to illustrate statistics and maps.
Florence Nightingale popularized the pie chart as a form of persuasion using statistics by calling attention to the mortality rates caused by poor sanitary conditions during the Crimean war.
How Does a Donut Chart Compare to a Pie Chart
Donut charts are similar to pie charts in that their aim is to illustrate proportions. However, they contain a blank center that can contain a description or another layer of information.
Another variation of a pie chart is known as a ring chart. A ring chart, also known as a sunburst chart, is a multi-layered donut chart with many rings to represent hierarchies of data in concentric circles.
How to Create a Pie Chart
- Start with what you want to illustrate. The main topic will be the title of your chart.
- Gather the data. Pie charts depict percentages. Make sure your percentages add up to 100% and get rid of any rounding issues that would make the total something other than 100%. SmartDraw allows you to write the percentage directly into a pie chart template or you can drag the edge of a wedge to make it bigger or smaller.
- Consider creating a legend. If a wedge is too small to hold text, you can create a label and draw a line identifying the appropriate slice. Alternatively, you can create a key that shows what each color represents.