Softonic

Box Plot Maker

Step 1 / 3 Box Plot Maker

Separate the numbers with commas, spaces or new lines. Write decimals with a point (2.5) and no thousands separators.

Next: chart style

Paste a list of numbers and the box plot maker draws a box and whisker chart for them: the box runs from the first quartile (Q1) to the third quartile (Q3), a line marks the median, the whiskers reach the lowest and highest values that are not outliers, and any outlier is drawn as its own dot. Below the chart you get the five-number summary, the IQR and the outlier fences, so you can check every mark on the plot. Choose a horizontal or vertical chart and download it as an SVG file for a report or a slide.

How to make a box plot

  1. 1

    Paste your numbers

    Type or paste at least two numbers, separated by commas, spaces or new lines. Entries that are not numbers are left out and listed on the result page.

  2. 2

    Choose the chart direction

    Pick a horizontal plot (values run left to right) or a vertical plot (values run bottom to top).

  3. 3

    Read the plot and the summary

    See the box plot with its axis, then the minimum, Q1, median, Q3, maximum, IQR, both fences and the list of outliers.

  4. 4

    Download or copy

    Download the chart as an SVG file or copy the summary as plain text. Start over to plot another data set.

How a box plot is built

A box plot compresses a data set into five numbers and shows how they sit on one number line.

Part of the plot What it shows
Left or bottom whisker end The smallest value that is not an outlier
Left or bottom edge of the box Q1, the first quartile: a quarter of the values lie below it
Line inside the box The median: half of the values lie below it
Right or top edge of the box Q3, the third quartile: a quarter of the values lie above it
Right or top whisker end The largest value that is not an outlier
Separate open dots Outliers, values beyond the fences

The box itself is the interquartile range, IQR = Q3 - Q1, which holds the middle half of the data.

The quartile method used here

This tool uses the inclusive median method. Sort the values, find the median, and split the list into a lower and an upper half. When the number of values is odd, the median itself is counted in both halves. Q1 is the median of the lower half and Q3 is the median of the upper half. This is the same rule that R’s fivenum() and boxplot() apply, and it is the one most textbooks teach for hand-drawn box plots.

Other programs can report slightly different quartiles for small samples. For the numbers 1 to 8, this tool gives Q1 = 2.5 and Q3 = 6.5, while Excel’s QUARTILE.INC gives 2.75 and 6.25. With a larger data set the methods move closer together.

Outliers and whiskers

The fences are Q1 - 1.5 x IQR and Q3 + 1.5 x IQR. A value outside a fence is plotted as a dot; a value exactly on a fence is not an outlier. Each whisker stops at the most extreme value that is still inside its fence, so a whisker never reaches an outlier.

Worked example

Data: 12, 15, 17, 18, 21, 22, 24, 25, 29, 64 (10 values).

  • Median: (21 + 22) / 2 = 21.5.
  • Lower half 12, 15, 17, 18, 21: Q1 = 17.
  • Upper half 22, 24, 25, 29, 64: Q3 = 25.
  • IQR: 25 - 17 = 8.
  • Fences: 17 - 12 = 5 and 25 + 12 = 37.
  • 64 is above 37, so it is an outlier. The upper whisker ends at 29 and the lower whisker at 12.

Tips

  • Use at least five or six values; a box plot of two or three points says very little.
  • Do not type thousands separators (write 1200, not 1,200).
  • The 1.5 x IQR rule marks values worth a second look. It does not prove that a value is an error.
  • To compare groups, make one plot per group and give them the same axis range.

Frequently Asked Questions

A box plot, also called a box and whisker plot, summarizes a data set with its minimum, first quartile, median, third quartile and maximum. The box covers the middle 50% of the values, the line inside it is the median, and the whiskers show how far the rest of the data reaches. Outliers are drawn as separate dots.

It uses the 1.5 x IQR rule. Any value below Q1 - 1.5 x IQR or above Q3 + 1.5 x IQR is drawn as a dot and listed under Outliers. A value that sits exactly on a fence is not counted as an outlier, and the whisker ends at the most extreme value inside the fences.

Quartile methods differ on small samples. This tool takes the median of the lower and upper halves and counts the median in both halves when the number of values is odd. Excel QUARTILE.INC interpolates between ranks instead, so for an even count such as 1 to 8 its Q1 and Q3 differ slightly. For an odd count the two usually agree.

Yes. The result page has a Download SVG button that saves the chart as a vector file with a white background. You can open it in a browser, drop it into a slide or document, or edit it in a vector editor. You can also copy the numbers as plain text.

The list can be up to about 12,000 characters, which is roughly two thousand typical numbers. You need at least two numbers to get a plot. Entries that are not numbers are skipped and reported on the result page so you can fix them.

The numbers are sent to our server to calculate the statistics and draw the chart, and they travel in the page link from one step to the next. Do not paste confidential data you would not put in a link. The SVG download is created on your device from the chart you see.

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