IQR Calculator — Interquartile Range
Enter your data values (leave extra boxes blank if you have fewer than 10) to calculate Q1, Q3, the interquartile range, and outlier fences.
What is the Interquartile Range?
The interquartile range (IQR) measures the spread of the middle 50% of a data set. It’s a robust measure of variability that isn’t thrown off by a few extreme outliers, which makes it useful for spotting unusual data points.
The Formula
The data is sorted and split at the median into a lower half and an upper half (excluding the middle value itself if the count is odd). Q1 is the median of the lower half, Q3 is the median of the upper half, and IQR = Q3 − Q1. Values below Q1 − 1.5×IQR or above Q3 + 1.5×IQR are commonly flagged as potential outliers.
- Enter at least two values; leave unused boxes blank.
- Values are sorted automatically — order doesn’t matter.
Provided for general statistical education and exploratory data analysis.