Bar Chart

A bar chart compares categories through bar length. Each bar starts from the same baseline, so a bar twice as long represents twice the value. Horizontal bars work well for rankings and long category names.

Visits by sourceSample data

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How to read a bar chart

Read the category label, then follow the bar to the value axis. In the example, Search has 420 visits and Email has 180. Search brings more than twice as many visits.

The categories are separate groups. They do not need to form a continuous sequence. This differs from a histogram, which groups numeric measurements into intervals.

Common forms

• Horizontal bars: leave room for category names and make rankings easy to scan.
• Columns: use vertical bars for short labels or a sequence of periods.
• Grouped bars: place two or more series beside each other, such as this month and last month.
• Stacked bars: split each bar into parts. The full length shows the total, but middle segments are harder to compare because they lack a shared baseline.

Set up a fair comparison

Start the value axis at zero. Cutting off the baseline makes differences in bar length look larger than they are. For small differences between large values, consider a dot plot with a clearly labeled scale.

Sort by value for a ranking. Keep time periods in date order and ordered categories in their natural order. Use one unit across all bars and equal bar widths.

Do not use a different color for every bar unless color identifies a group. Label important values directly, and provide the data for readers who need exact numbers.