Outlier Calculator
Enter your data values to find outliers using the standard interquartile range (IQR) method.
What this calculator does
This calculator flags outliers in your dataset using the interquartile range (IQR) method, one of the most widely used rules of thumb in exploratory statistics.
How the calculation works
The calculator sorts your data and finds the first quartile (Q1) and third quartile (Q3), then computes the IQR as Q3 minus Q1. Any value below Q1 – 1.5×IQR or above Q3 + 1.5×IQR is flagged as an outlier. This 1.5×IQR rule is the standard convention used in box plots.
Enter at least 4 values for a meaningful quartile calculation. Flagged outliers are not automatically errors — they may be genuine extreme observations worth investigating rather than removing. This tool is for general and educational statistical use.