How to find quartiles
- Type or paste your numbers, separated by commas, spaces or new lines. They don’t need to be in order.
- Pick the method your class, calculator or spreadsheet uses. The default matches the TI-84 and most textbooks.
- Read Q1 and Q3, the median, the interquartile range and the five-number summary. Outliers beyond 1.5 × IQR are listed and drawn as circles on the box plot.
Reading a box plot
The box holds the middle 50% of the data. A long box means the middle values are spread out; a median line off-centre means the data is skewed. Whiskers show how far the rest reaches, and separate circles mark outliers worth a second look, whether they are typing mistakes or genuinely unusual results.
Quartiles and percentiles
Q1 is the 25th percentile, the median the 50th and Q3 the 75th. Exam boards, salary surveys and growth charts often report the quartiles because they describe a typical range without being thrown off by a few extremes. For the mean, mode and standard deviation of the same numbers, use the average calculator.