Range Chart
Displays the spread between a minimum and maximum value for each category using a bar or line segment — ideal for showing variability, confidence intervals, or daily temperature ranges.
// 01 — The chart
What it looks like
A range chart showing the daily temperature spread (low to high) for each month. The highlighted bar (July) shows the widest variation and highest temperatures.
// 02 — Definition
What is a range chart?
A range chart (also known as a span chart or floating bar chart) displays the spread between two values for each category. Unlike a standard bar chart where bars start at zero, range chart bars “float” between their minimum and maximum values.
The bar’s position shows the absolute level (where on the scale the values fall), while the bar’s height (or width, if horizontal) shows the spread or uncertainty. This dual encoding is the range chart’s superpower — it shows both the level and the variability of each category in one view.
Range charts are commonly used in weather visualization (daily high/low temperatures), finance (daily price ranges), and statistics (confidence intervals). They answer the question: “Not just what is the value, but how variable is it?”
// 03 — Anatomy
Parts of a range chart
// 04 — Usage
When to use it — and when not to
- Showing variability (min/max) per category, not just averages
- Displaying confidence intervals or uncertainty ranges
- Comparing daily temperature highs and lows across months
- The spread itself is the key insight, not individual values
- You only have one value per category — use a standard bar chart
- You need to compare specific individual data points — use a dot plot
- The audience expects bars starting from zero and may be confused by floating bars
- You want to show the full distribution shape — use a box plot or violin plot
// 05 — Reading guide
How to read a range chart
Note that bars float
Unlike standard bars, range bars don't start at zero. The bottom edge is the minimum; the top edge is the maximum.
Compare bar heights
Taller bars mean wider ranges (more variability). Short bars mean the min and max are close together.
Check bar positions
Higher-positioned bars indicate higher overall values, even if the spread is the same.
Look for overlaps
When bars overlap vertically, the categories have values in a similar range. Non-overlapping bars indicate clear separation.
// 06 — Pitfalls
Common mistakes
Not explaining the floating bars
Readers expect bars from zero. Add a subtitle or annotation clarifying that bars show min-max ranges.
Confusing with error bars
Error bars show uncertainty around a point estimate. Range bars show actual min/max values. Label clearly.
No midpoint marker
Adding a median or mean marker inside each bar helps readers see both the center and the spread.
Too many categories
Beyond 12–15 categories, the chart becomes dense. Consider grouping or filtering.
// 07 — Examples
Real-world examples
Daily high/low temperature ranges by month for a city
Daily stock price ranges (high/low) across trading days
Confidence intervals for measured quantities across experiments
Scoring range (best to worst game) per player across a season
// 08 — Quick reference
Key facts
| Also known as | Span chart, floating bar chart, high-low chart |
| Primary use | Showing min-max spread per category |
| Data types | One categorical + two quantitative values (min and max) |
| Zero baseline | Not required (bars float) |
| Best category count | 4–15 |
| Common domains | Weather, finance, statistics |
// 09 — Data format
What your data should look like
| Column | Type | Description |
|---|---|---|
| Category | String | Label for each range bar (e.g., month, product) |
| Min | Number | The lower bound of the range |
| Max | Number | The upper bound of the range |
Jan, 28, 40
Feb, 30, 44
Jul, 72, 90
Dec, 32, 44
// 10 — Construction
How to build a range chart
Set the value axis
Choose a scale that covers the full range of all categories' min and max values.
Lay out categories
Space categories evenly along the X-axis (vertical bars) or Y-axis (horizontal bars).
Draw floating bars
For each category, draw a rectangle from the min value to the max value. The bar does not touch zero.
Optionally add midpoint markers
A small line or dot at the median or mean within each bar adds context.
Add axis labels and title
Clearly label units and provide a subtitle explaining that bars show ranges, not totals.
// 11 — Accessibility
Accessibility notes
Explain floating bars in text
Add a subtitle or annotation explaining that bars don't start at zero — they show a min-max range.
Provide a data table
Include a table with category, min, max, and range size for screen-reader users.
Use ARIA labels
Each bar should have an aria-label like "July: low 72°F, high 90°F, range 18°F."
Ensure highlighted bars are accessible
If colour distinguishes a highlighted bar, also use a border, pattern, or label.
// 12 — Variations
Variations
Range area chart
Fills the area between two lines on a time axis to show range over time
Range with midpoint
Adds a marker (dot or line) inside each bar for the mean or median
Horizontal range bar
Categories on Y-axis with floating bars extending horizontally
Range column chart
Vertical floating bars — the most common orientation
// 10 — FAQs
Frequently asked questions
What is a range chart?+
A range chart (also known as a span chart or floating bar chart) displays the spread between two values for each category. Unlike a standard bar chart where bars start at zero, range chart bars "float" between their minimum and maximum values.
When should you use a range chart?+
Use a range chart when showing variability (min/max) per category, not just averages. It also works well when displaying confidence intervals or uncertainty ranges, and when comparing daily temperature highs and lows across months.
When should you avoid a range chart?+
Avoid a range chart when you only have one value per category — use a standard bar chart. It is also a poor fit when you need to compare specific individual data points — use a dot plot, or when the audience expects bars starting from zero and may be confused by floating bars.
How is a range chart different from a dumbbell chart?+
Both a range chart and a dumbbell chart can look similar at first glance, but they answer different questions. Reach for a range chart when the comparisons and patterns it was designed to reveal match what you need to communicate, and choose a dumbbell chart when its particular strengths better fit your data and audience.
Are range charts accessible to screen readers?+
Yes — a range chart can be made accessible to screen readers by pairing it with a clear text summary of the key insight, ensuring color choices meet WCAG contrast guidelines, adding descriptive alt text or aria-label to the SVG, and offering the underlying data as an HTML table fallback for assistive technologies.
Is a range chart suitable for dashboards?+
Yes — a range chart can work well in dashboards as long as the panel is large enough for readers to perceive the encoded values, has a clear title, and includes the legend or axis labels needed to interpret it.