Calculate percentile rank, quartiles, IQR, and visualize with box plots
A percentile is a value below which a certain percentage of observations fall. For example, if you scored in the 75th percentile on a test, you scored better than 75% of test takers.
IQR = Q3 - Q1
The IQR measures the spread of the middle 50% of the data. It's resistant to outliers and is commonly used to identify outliers:
A concise summary of data distribution consisting of:
This calculator uses the linear interpolation method (Excel/R method):
Enter your data and click calculate to see results
Every coffee helps keep the servers running. Every book sale funds the next tool I'm dreaming up. You're not just supporting a site — you're helping me build what developers actually need.
A percentile (e.g., 90th) is the value below which a given percentage of observations fall; percentile rank is the percentage position of a given value within the data.
Data are sorted ascending; index is typically (p/100)·(n+1). If non‑integer, interpolate. Methods vary; we use a common linear interpolation approach.
Quartiles split data into four equal parts: Q1 (25th), Q2/median (50th), Q3 (75th). IQR = Q3 − Q1 is a robust spread measure used for outlier detection.
A common rule flags values below Q1 − 1.5·IQR or above Q3 + 1.5·IQR as potential outliers. Context matters — not all flagged points are errors.