Outlier Calculator
Find outliers in a data set with the 1.5 × IQR rule, with the quartiles and fences.
Change the values and press Calculate to work out your own figures.
Enter numbers to find any that lie unusually far from the rest.
Show the working
- Quartiles (median of each half (the middle value left out when the count is odd)): Q1 = 3, Q3 = 8
- IQR = 5; 1.5 × IQR = 7.5
- Lower fence = Q1 − 1.5 × IQR = -4.5
- Upper fence = Q3 + 1.5 × IQR = 15.5
How to use it
Enter numbers to find any that lie unusually far from the rest.
Paste or type the numbers separated by commas, spaces or new lines. Results are worked out exactly and shown to 12 significant figures; Show the working lists each step.
Key facts
lower fence = Q1 − 1.5 × IQR; upper fence = Q3 + 1.5 × IQR
Is an outlier a mistake?
Not necessarily. An outlier is unusual, not wrong: check it, and keep it if it's a genuine measurement.
Questions
What is the 1.5 IQR rule?
Values more than 1.5 interquartile ranges below Q1 or above Q3 are flagged as outliers.
Should I delete outliers?
Only if they are errors.
Formulas
lower fence = Q1 − 1.5 × IQR; upper fence = Q3 + 1.5 × IQR
Sources
Limitations
- Up to 5,000 values. Values are separated by commas, spaces or new lines, so write 1250 rather than 1,250.