Outlier Calculator
IQR fences and z-scores flag unusual points instantly.
Enter your values
Enter the data values you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Outliers (1.5 × IQR)
- 42
- Lower fence
- 9.5
- Upper fence
- 23.5
- Q1 / median / Q3
- 14.75 / 15.5 / 18.25
- IQR
- 3.5
- Outliers by z-score > 3
- None found
- Data without outliers
- 12, 14, 15, 15, 16, 18, 19
Quick answer
A point is a mild outlier when it falls more than 1.5 × IQR below Q1 or above Q3, and an extreme outlier beyond 3 × IQR.
fences = Q1 − 1.5·IQR and Q3 + 1.5·IQR
At a glance
| What it does | IQR fences and z-scores flag unusual points instantly. |
|---|---|
| Category | Statistics |
| Inputs needed | Data values |
| Main output | Outliers (1.5 × IQR) |
| Formula | fences = Q1 − 1.5·IQR and Q3 + 1.5·IQR |
| Cost | Free — no sign-up, no download |
How to use the Outlier Calculator
- 1Paste your dataset separated by commas.
- 2Check which points fall outside the fences.
- 3Decide whether each outlier is a genuine extreme value or a data-entry error before deleting anything.
Inputs explained
- Data values
- Enter the data values you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Data values12, 14, 15, 15, 16, 18, 19, 42
Results
- Outliers (1.5 × IQR)42
- Lower fence9.5
- Upper fence23.5
- Q1 / median / Q314.75 / 15.5 / 18.25
- IQR3.5
- Outliers by z-score > 3None found
- Data without outliers12, 14, 15, 15, 16, 18, 19
Frequently asked questions
Should I always remove outliers?
No. Remove them only when you can show they are errors. Genuine extremes often carry the most interesting information.
IQR rule or z-scores?
IQR is safer for small or skewed samples because the mean and SD are themselves dragged around by outliers.
What do I need to enter into the Outlier Calculator?
Just 1 value: data values. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Outlier Calculator work out the answer?
A point is a mild outlier when it falls more than 1.5 × IQR below Q1 or above Q3, and an extreme outlier beyond 3 × IQR. It applies the formula fences = Q1 − 1.5·IQR and Q3 + 1.5·IQR and shows the working so you can check each step by hand.
Is the Outlier Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.