Bar graph
Use for: Amounts across categories: sales by product, votes by party. Horizontal for long names; grouped or stacked for several series.
Avoid for: Continuous ranges (use a histogram).
Types of charts and when to use each
Start with the question you want to answer, not the chart. Pick the question below and you have the chart type, with a free maker for each.
Five questions, fourteen charts
Almost every chart answers one of five questions: comparison, composition, change over time, distribution or relationship. This grouping follows the classic chart-chooser approach popularised by Andrew Abela and used in the Financial Times’ “Visual Vocabulary”.
Try the chooser, or scroll for the full list.
Which chart should you use?
Use a bar graph. Bar lengths are the easiest visual to compare precisely.
Comparison
How big is each thing, compared with the others?
Radar chart
Use for: Profiles of 2–3 items across 5–8 measures on the same scale.
Avoid for: Precise comparisons or measures on different scales.
Composition
What is the whole made of?
Pie chart
Use for: 2–6 parts of one total, like a budget or market share.
Avoid for: Many small slices, or answers that don’t add to a whole.
Donut chart
Use for: Same as a pie, with the total or a headline number in the centre.
Avoid for: Same as a pie.
Area chart
Use for: How a total and its parts change over time (stacked or 100%).
Avoid for: Negative values; precise reading of middle layers.
Change over time
Is it going up, down or round in circles?
Line graph
Use for: Trends across ordered time points; several series as several lines.
Avoid for: Unordered categories.
Gantt chart
Use for: Project tasks as bars on a timeline.
Avoid for: Numeric data; it shows durations only.
Distribution
How are the values spread out?
Histogram
Use for: The shape of one numeric variable: skew, peaks, spread.
Avoid for: Tiny data sets (use a dot plot).
Box plot
Use for: Median, quartiles and outliers, especially comparing groups.
Avoid for: Showing a two-peaked shape (a box hides it).
Dot plot
Use for: Small data sets where every value should be visible.
Avoid for: Hundreds of values.
Stem-and-leaf
Use for: Small data sets on paper or in class: sorted list and shape in one.
Avoid for: Large or very spread data.
Relationship
Do two (or three) things move together?
Scatter plot
Use for: Two numbers per case; add a line of best fit for the trend.
Avoid for: Time series with one value per date (use a line).
Bubble chart
Use for: Three numbers per case: x, y and size.
Avoid for: More than ~25 bubbles.
Venn diagram
Use for: Overlap between 2–3 groups of named items.
Avoid for: Four or more sets.
Questions
What are the most common types of charts?
Bar graphs, line graphs and pie charts cover most everyday needs. Histograms, scatter plots and box plots are the main statistical charts.
What is the difference between a chart and a graph?
In everyday use they are interchangeable. Some teachers reserve “graph” for plots on x–y axes (line graphs, scatter plots) and “chart” for the rest (pie charts, Gantt charts).
Which chart is best for comparing data?
A bar graph for comparing values across categories; a grouped bar graph or several lines for comparing groups over time; a box plot for comparing distributions.