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Box Plot Maker

Visualize spread, quartiles, and outliers — compare groups at a glance

A box-and-whisker plot packs five key statistics into one compact picture: the minimum, first quartile (Q1), median, third quartile (Q3), and maximum. The box spans the interquartile range (IQR = Q3 − Q1), and dots beyond the whiskers are outliers.

This tool loads 40 exam scores from four different class sections. Click Link Data to draw a grouped box plot comparing all four sections at once. You'll instantly see which section had higher median scores and which had more spread.

Paste your own CSV with a numeric column and optional group column to analyze your own data.

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FAQ

What do the parts of a box plot mean?
The box spans Q1 to Q3 (the middle 50% of data). The line inside is the median. The whiskers extend to the most extreme values within 1.5×IQR of the box edges. Points beyond the whiskers are outliers.
What is the IQR?
IQR (interquartile range) = Q3 − Q1. It measures the spread of the middle 50% of data, making it resistant to outliers. A large IQR means high variability; a small IQR means the data clusters tightly around the median.
How do I spot outliers with a box plot?
Any point below Q1 − 1.5×IQR or above Q3 + 1.5×IQR is flagged as an outlier and drawn as an individual dot beyond the whisker. These often deserve investigation — they may be data entry errors or genuinely extreme cases.
When is a box plot better than a histogram?
Box plots shine when comparing multiple groups side by side — one box per group gives an instant visual comparison of medians and spread. Histograms are better for seeing the full shape of a single distribution.

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Statistics CalculatorHistogram MakerData & GraphsRegression Calculator