# Quartile

> A chart word, with the charts that use it.

**Definition.** Quartiles are the values that cut sorted data into four equal parts; the box in a box plot. The box spans the middle half, from the first quartile to the third.

Updated Nov 2, 2026

## 043 · Box plot

- **01 The box.** From the first to the third quartile: the middle half.
- **02 The median.** The second quartile, inside the box.

## Where you see it

- [043 · Box plot](https://usechartory.com/charts/box-plot): Distribution · AI data

## Common mistakes

- **Reading the box as the full range** The box is the middle half. The whiskers and dots show the rest.
- **Box plots with few values** Quartiles of five values say little. Show the points instead.

## Questions

### What are Q1, Q2 and Q3?

The values a quarter, half and three quarters of the sorted data sit below.

### Why show quartiles instead of the range?

They ignore the extremes, so the typical spread reads clearly.

## Related terms

- [Median](https://usechartory.com/glossary/median): The middle value: half the data sits above it, half below.
- [Whisker](https://usechartory.com/glossary/whisker): The line from a box to the lowest and highest values that are not outliers.
- [Outlier](https://usechartory.com/glossary/outlier): A value far from the rest, drawn on its own so it is not hidden.
- [Distribution](https://usechartory.com/glossary/distribution): How values spread across a range: where they cluster and where they thin out.

## Box plot and the other types.

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