Treemap
Also called: Tree map, Treemap chart
A treemap splits a rectangle into smaller rectangles sized by value, such as revenue by product, to show how a total breaks down. Nested rectangles show a hierarchy.
How to read a treemap
The whole rectangle is the total, here $10.0M of revenue. Each smaller rectangle is one part, and its area is its share: Laptops takes up 36% of the space because it’s 36% of revenue.
Most tools lay the rectangles out largest first, starting in one corner, and try to keep them close to square so they’re easier to compare. Ben Shneiderman introduced treemaps around 1990 to show disk usage, and the idea carried straight over to business data.
Nested treemaps
A treemap’s real strength is hierarchy. Put rectangles inside rectangles and you see both levels at once.
Here you can see that North America is the biggest region and that most of it is one country, while EMEA is spread evenly across three.
Common uses
Ordered from most to least common.
- Revenue or sales by product or category, often nested (category → product).
- Spend by department or cost centre, where finance wants to see the big buckets and what’s in them.
- Revenue by geography, region → country, as above.
- Share of anything with many parts: support tickets by topic, traffic by page, storage by folder.
In Power BI vs. Tableau
| Power BI | Tableau | |
|---|---|---|
| Built-in | Treemap | Treemap in Show Me |
| Size | Values field | Measure on Size |
| Nesting | Category + Details fields, with drill-down | More than one dimension on the Marks card |
Best practices
- Label the big rectangles with name, value and share. Let the small ones go unlabelled and rely on tooltips.
- Use one colour family, darker for bigger or for the parent group, and grey for “Other”.
- Group the tail into “Other” so thin slivers don’t clutter the edge.
- Don’t use it for change over time. Rectangles shift position between periods, so readers can’t track them. Use stacked columns instead.
- Avoid negative values. Area can’t be negative, so losses or refunds won’t show.
Mocking up a treemap
Treemaps get awkward fast in a short, wide dashboard slot: the small rectangles collapse into slivers. Try it at its real size on a mockup and decide which levels to show before you build.