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Box Plot Maker

Paste your numbers (one data set or several) and get a clean box-and-whisker plot with the five-number summary, interquartile range and outliers marked. Compare groups side by side and download the chart as PNG or SVG.

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How to use the Box Plot Maker

  1. Paste your data: numbers separated by commas, spaces or new lines. For several groups, put each group on its own line (optionally starting with a name and a colon) or paste columns from a spreadsheet.
  2. Choose the quartile method your class or software uses and the whisker rule (1.5 × IQR or min/max).
  3. Style the chart: orientation, title, axis label, mean marker, data points and colors.
  4. Read the statistics table under the chart for the five-number summary, IQR, fences and outliers.
  5. Download PNG or SVG for your report, or copy the statistics as CSV.

How to read a box and whisker plot

  • Box: spans from Q1 (25th percentile) to Q3 (75th percentile), so it holds the middle 50% of the values. Its length is the interquartile range, IQR = Q3 − Q1.
  • Line in the box: the median (50th percentile). If it sits closer to one end, the middle half of the data is skewed.
  • Whiskers: reach the smallest and largest values inside the fences Q1 − 1.5 × IQR and Q3 + 1.5 × IQR.
  • Dots: outliers beyond the fences. Open dots are mild outliers; filled dots lie more than 3 × IQR from the box (extreme outliers).
  • ×: the mean. A mean far from the median signals skew or outliers.

Worked example: computing the five-number summary

Data (n = 11, sorted): 3, 7, 8, 9, 10, 12, 13, 14, 15, 17, 40

StepMedian of halves (TI-84)Excel QUARTILE.INC
Median12 (6th value)12
Q1median of 3, 7, 8, 9, 10 = 8position (11 − 1) × 0.25 = 2.5 → 8.5
Q3median of 13, 14, 15, 17, 40 = 15position 7.5 → 14.5
IQR15 − 8 = 714.5 − 8.5 = 6
Fences−2.5 and 25.5−0.5 and 23.5
Outliers4040
Whiskers3 to 173 to 17

Both methods are correct; they simply define quartiles differently. Choose the one your course or software uses so your numbers match. For large data sets the methods give nearly the same result.

Data formats you can paste

  • One data set: 12, 15, 9, 22, 17 or one number per line (a column copied from a spreadsheet).
  • Several data sets, one per line: Before: 12 15 9 22 and After: 14 18 11 25. A name followed by a colon labels the box.
  • Spreadsheet columns: copy several columns with names in the first row; each column becomes one box. Empty cells are ignored, so columns can have different lengths.

Need just the numbers? The Five Number Summary Calculator and the Outlier Calculator show the steps in detail, and the Histogram Maker shows the shape of the distribution.

Frequently asked questions

What does a box plot show?

A box plot (box-and-whisker plot) shows the five-number summary of a data set. The box runs from the first quartile (Q1) to the third quartile (Q3), the line inside it is the median, and the whiskers reach out to the smallest and largest values that are not outliers. Points beyond the whiskers are outliers.

How are outliers determined?

With the standard Tukey rule, the interquartile range is IQR = Q3 − Q1. Values below Q1 − 1.5 × IQR or above Q3 + 1.5 × IQR are outliers and are drawn as separate dots. Values beyond 3 × IQR from the box are often called extreme outliers and are drawn as filled dots here.

Why are my quartiles different from my calculator or Excel?

There are several accepted ways to compute quartiles. The TI-84 and most textbooks take the median of the lower and upper halves (excluding the median when n is odd). Excel's QUARTILE.INC interpolates using (n − 1) × p, and QUARTILE.EXC uses (n + 1) × p. Pick the matching method in the Quartiles menu.

How do I make side-by-side box plots?

Put each group on its own line, for example 'Class A: 72, 85, 90' and 'Class B: 65, 70, 88', or paste several columns from a spreadsheet with the group names in the first row. All boxes share one axis so they can be compared directly.

What is the interquartile range (IQR)?

The IQR is Q3 minus Q1: the width of the box. It contains the middle 50% of the data and, unlike the range, is not affected by extreme values, which makes it a robust measure of spread.

How many values do I need?

You can draw a box plot from a single value, but quartiles become meaningful from about 5 values upward. Non-numeric entries are skipped and reported, so you can paste data with stray text.

Is my data uploaded?

No. All calculations and the chart are done in your browser with JavaScript. Your data is only kept in your browser's local storage so it is still there when you return.

Are all the tools on FreeToolCabin tested for quality and accuracy?

Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.

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