How to make a box plot
- Each column is a group. Rename the headers (for example “Class A”, “Class B”) and add columns with Add data series.
- Paste or type the raw observations for each group, one per row. Groups can have different numbers of values; leave unused cells blank.
- Choose the quartile method and whisker rule in Customize → Chart options.
- Optionally show the mean (×) and every data point.
- Check the five-number summary under View chart data as a table, then download.
Data format
| Column | Type | Notes |
|---|---|---|
| Data series (one column each) | Number | 1–12 columns; blank cells allowed |
Up to 5,000 rows. Each column is one group and each row holds one raw observation. Groups can have different numbers of values — leave unused cells blank. Quartiles, whiskers and outliers are calculated for you.
Customization options
- Quartile method: inclusive (Excel QUARTILE.INC) or exclusive (QUARTILE.EXC).
- Whiskers: 1.5 × IQR with outliers drawn as dots, or minimum to maximum.
- Mean marker and an optional overlay of every data point (with deterministic jitter).
- Box width, colors, axis range and titles.
Downloading and exporting
- PNG: best for slides, documents and the web. It supports transparent backgrounds, and you can choose standard, 2×, 4× or slide-sized (1920 × 1080) output.
- JPEG: a smaller file with a solid background.
- SVG: a true vector file. It stays sharp at any size and can be edited in Illustrator, Inkscape or Figma.
- PDF: vector PDF sized to the chart, A4 or US Letter. If your labels use characters outside the standard PDF fonts (for example Chinese, Arabic or emoji), the PDF uses a high-resolution image instead and tells you.
- CSV and .json: your data, or the whole chart with its settings, to re-open later.
When to use a box plot
- Comparing the distribution of a measurement across groups, such as test scores by class or delivery times by courier.
- Showing spread and skew, not just the average.
- Spotting outliers quickly.
When to choose a different chart
- Each group has fewer than about five values. The quartiles become unreliable, so plot the points with a scatter plot.
- The distribution has two peaks. A box plot hides bimodality; check with a histogram.
- Your audience is unfamiliar with box plots. Add a subtitle explaining the box and whiskers, or use bars with error ranges.
Common mistakes to avoid
Entering summary statistics as data
This tool calculates the statistics from raw observations. Typing min, Q1, median, Q3 and max as five data points produces a box plot of those five numbers, not of your original data.
Assuming whiskers show min and max
With the 1.5 × IQR rule, whiskers stop at the most extreme value within the fences, and anything beyond is drawn as an outlier. State the rule in your caption.
Comparing medians without considering spread
Two groups with different medians but heavily overlapping boxes may not be meaningfully different.
Practical examples
Test scores by class
Three classes with 12–13 students each. Class B has the lowest median and one high outlier at 95.
Response times
API latency for three server regions, showing that one region has a long tail of slow requests.
Plant growth
Heights under three fertilizer treatments, with all points overlaid.
How quartiles and whiskers are calculated
Inclusive quartiles (the default) use linear interpolation between ranked values at position (n − 1) × p, the same method as Excel’s QUARTILE.INC, R’s default type 7 and NumPy’s default. Exclusive quartiles use position (n + 1) × p, matching QUARTILE.EXC. The two methods can give slightly different boxes for small samples, so if you need to match another program, choose the same method.
With the Tukey rule, the interquartile range is IQR = Q3 − Q1. Values below Q1 − 1.5 × IQR or above Q3 + 1.5 × IQR are outliers, and whiskers extend to the most extreme non-outlier values.
Frequently asked questions
What does the box represent?
The box spans the first quartile (Q1) to the third quartile (Q3), which contains the middle 50% of the data. The line inside is the median.
How are outliers defined?
With the default 1.5 × IQR rule, any value more than 1.5 interquartile ranges below Q1 or above Q3 is drawn as a separate dot.
Can groups have different sample sizes?
Yes. Leave unused cells blank. Each group’s n is shown in the summary table and tooltip.
Why do my quartiles differ from another program?
There are several quartile definitions. Switch between inclusive and exclusive to match Excel’s QUARTILE.INC or QUARTILE.EXC.
Can I enter the five-number summary directly?
Not currently. The tool works from raw observations so that outliers and the mean are correct.
Your data stays private
Charts are drawn by your browser. Your data isn’t uploaded to our servers; it is kept only in this browser’s storage, for autosave and saved charts, until you clear it. See our privacy policy.