Box Plot Maker
Box-and-whisker plots with quartiles, IQR and outliers; compare sets, download SVG/PNG.
About this tool
Type one data set per line, with an optional name before a colon, for example Class A: 62, 68, 71. The tool draws every set on the same axis, lists the minimum, Q1, median, Q3, maximum, IQR and mean, and flags outliers. Download the chart as SVG for documents or PNG for slides.
How to read a box plot
A box-and-whisker plot squeezes a whole data set into five numbers. The box runs from the first quartile (Q1) to the third quartile (Q3), so it holds the middle half of the data. Its length is the interquartile range (IQR), and the line inside it is the median. The whiskers stretch to the furthest values that are still within 1.5 ร IQR of the box. Anything further out is drawn as a separate dot and treated as an outlier, which is Tukey's rule. In the example, Class B has Q1 68, median 73 and Q3 77. That gives an IQR of 9 and an upper fence of 77 + 13.5 = 90.5, so the score of 99 is shown as an outlier. Box plots are good for comparing groups side by side: a higher median, a narrower box or a longer whisker each tell you something at a glance. They hide detail, though. Two very different shapes, such as one with two peaks, can produce the same box, so pair a box plot with a histogram when the shape matters. Honest limits: quartiles use the common linear-interpolation method (Excel QUARTILE.INC). Some textbooks use a different method, which can move Q1 and Q3 slightly for small samples. The percentile calculator and the standard deviation calculator are related.
Frequently asked questions
What do the parts of a box plot mean?
The box spans Q1 to Q3 (the middle 50%), the line inside is the median, the whiskers reach the furthest non-outlier values, and dots are outliers.
How are outliers found in a box plot?
Any value more than 1.5 ร IQR below Q1 or above Q3 is an outlier under Tukey's rule.
Can I compare several groups?
Yes. Put each group on its own line and they're drawn on a shared axis.
Is my data uploaded?
No. The chart is drawn in your browser and nothing is stored or sent.