Statistics Calculators

Interquartile Range (IQR) Calculator

Calculate the first quartile (Q1), third quartile (Q3) and interquartile range (IQR) of a dataset.

Q1 (25th percentile) —

Q3 (75th percentile) —

Interquartile range (IQR) —

About the Interquartile Range (IQR) Calculator

The interquartile range (IQR) measures the spread of the middle 50% of a dataset. It's found by splitting the sorted data at the median into a lower and upper half, then taking the median of each half as Q1 and Q3.

Formula: IQR = Q3 − Q1, where Q1 is the median of the lower half and Q3 is the median of the upper half of the sorted data

Because it ignores the most extreme 25% on each end, the IQR is a robust measure of spread that isn't distorted by outliers, and is used to construct box plots and detect outliers (values beyond 1.5 × IQR from Q1 or Q3).