When can you use a circle graph instead of a bar graph?

A circle graph, or pie chart, is best used when you want to represent parts of a whole, showing the relative proportions of different categories as slices of a circle. It's effective for displaying data with a limited number of categories, particularly when those categories sum to a meaningful total, such as percentages. In contrast, a bar graph is more suitable for comparing quantities across different categories or showing changes over time. Therefore, choose a circle graph when emphasizing the relationship of parts to a whole is more important than comparing individual values.