About the Box Plot Maker
Box Plot Maker draws a box-and-whisker plot from your numbers. Paste one, two or three sets of data and the page finds the minimum, first quartile, median, third quartile and maximum, draws a box from Q1 to Q3 with a line at the median, extends the whiskers to the furthest values within 1.5 times the interquartile range and marks any outliers with circles. Choose how the quartiles are found, to match your textbook or spreadsheet, and download the picture as a PNG or SVG. The summary numbers are listed under the plot.
Updated October 2026
How to use the Box Plot Maker
- 1Choose how many data sets you want to compare, from one to three.
- 2Name each set and paste its numbers.
- 3Pick the quartile method that your course uses.
- 4Check the plot and the summary numbers.
- 5Download the PNG or SVG.
Anatomy of a box plot
The box covers the middle half of the data, from Q1 to Q3, and its width is the interquartile range. The line inside is the median. The whiskers go out to the smallest and largest values that are not outliers, and the circles beyond are the outliers. At a glance you see the centre, the spread and the symmetry of the data.
Comparing groups
Place several box plots on one scale to compare them. If the boxes barely overlap, the groups differ. If one box is much longer, that group is more spread out. If the median line sits near one end of its box, the data is skewed.
- Median higher in one group: that group tends to have larger values
- Longer box or whiskers: more variation
- Circles: unusual values to check for errors
Choosing the quartile method
Different books and tools compute quartiles slightly differently, so your Q1 and Q3 may differ from someone else's by a small amount. The first two options split the data into halves, with or without the middle value, and the third uses Excel's QUARTILE.INC rule. Use the same method throughout an assignment.
Related tools
Compute the numbers without the picture using the Quartile Calculator, find averages with the Average Calculator and spread with the Standard Deviation Calculator, and see the data as a Stem and Leaf Plot Generator display.
Features
- One to three data sets side by side
- Median, quartiles, whiskers and outliers
- Three quartile methods
- Summary numbers under the plot
- PNG and SVG download
- Private: nothing is uploaded
Frequently asked questions
What is a box plot?
A picture of the spread of data: a box from the first to the third quartile, a line at the median and whiskers that reach the lowest and highest values that are not outliers.
What are outliers here?
Values more than 1.5 times the interquartile range (IQR) below Q1 or above Q3. They are shown as separate circles.
Why do quartile methods differ?
There is more than one rule to find Q1 and Q3. Some leave the middle value out when the count is odd, some keep it, and spreadsheets use interpolation. Use the one your course or software uses.
How many numbers do I need?
At least two per data set. A box plot of very few values is not very informative.
Can I compare groups?
Yes. Add a second and third data set to see them on the same scale.
How do I read the median?
It is the line inside the box. Half of the values are below it and half above.
Can I use the image in a report?
Yes. The PNG has a white background and is twice the on-screen size for sharp printing.
What if my data has only a few values?
The plot is drawn with as few as two values, but with so few points the quartiles are rough. Add more data for a more reliable picture.
Can I use the plot for non-numeric data?
No. A box plot needs numbers. For categories use a bar chart, such as the one made by the Chart Maker.
Is my data uploaded?
No. The plot is drawn in your browser.