When to use this calculator
Measure the spread of the middle half of a dataset. Uses inclusive linear interpolation for both quartiles.
Explore the descriptive statistics calculators for other questions in this topic. For a related calculation, use the Mean Absolute Deviation Calculator: Find mean absolute distance from the arithmetic mean.
PUTTING IT INTO PRACTICE
Interquartile Range: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Data values | 1,2,3,4,5 |
| Result | 2 |
- Check the input labels and enter the example values above.
- Apply the relationship: IQR = inclusive 75th percentile − inclusive 25th percentile..
- The result is 2 , rounded for display.
How to interpret your result
Uses inclusive linear interpolation for both quartiles.
The mean, median, range and standard-deviation tools accept variable-length lists with their limits stated. Choose a sample or population denominator appropriately. A summary statistic does not validate the sampling process or explain causation.
Frequently asked questions
Should I use sample or population standard deviation?
Use population deviation for the complete population being described. Use the sample form when estimating variability from a sample under suitable assumptions.
When is the interquartile range calculator useful?
Measure the spread of the middle half of a dataset. Uses inclusive linear interpolation for both quartiles.
How do I use the interquartile range calculator?
Enter data values. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
IQR = inclusive 75th percentile − inclusive 25th percentile..
What should I check before using the result?
Uses inclusive linear interpolation for both quartiles.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see NIST: exploratory data analysis ↗. This is a topic reference, not an external review or endorsement of this tool.
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