Box Plot Calculator
Build a box-and-whisker plot summary with quartiles, fences, and outliers.
Table of Contents
How to Use
- Enter your numerical observations separated by commas, spaces, or semicolons.
- Select calculate to generate the five-number summary, IQR, fences, and whiskers.
- Review the outlier section to see values flagged outside the 1.5 × IQR fences.
Understanding Box-and-Whisker Plots
A box plot (box-and-whisker plot) summarizes a dataset using its quartiles. The box spans the interquartile range (IQR) from Q1 to Q3, and the line inside the box marks the median.
- Lower whisker extends to the smallest data point within the lower fence.
- Upper whisker extends to the largest data point within the upper fence.
- Points beyond the fences are plotted individually as potential outliers.
Why the IQR Matters
The interquartile range captures the middle 50% of the data and resists the influence of extreme values. Fences computed with 1.5 × IQR offer a standard rule-of-thumb for highlighting unusual observations.
Frequently Asked Questions
- What if my dataset has fewer than 5 values?
- Box plots rely on quartiles, which need several data points to be meaningful. Collect more observations or use the five-number summary calculator for small datasets.
- Are outliers always errors?
- Not necessarily. Outliers may indicate interesting variation or data-entry mistakes. Use the flagged values as a starting point for investigation.
- Can I change the outlier rule?
- This calculator uses the classic 1.5 × IQR rule. If your analysis requires different multiples, adjust the fences manually using the reported IQR.