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Free quartile calculator for descriptive statistics. Enter dataset values to compute first quartile (Q1), median (Q2), third quartile (Q3), and interquartile range (IQR) instantly.
Last updated: April 20, 2026
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Q1 (25th percentile)
6.0000
Q2 (median)
12.0000
Q3 (75th percentile)
16.0000
Interquartile range (IQR)
10.0000
Min
3.0000
Count
9
Max
21.0000
Interpretation
The middle 50% of values lie between 6.0000 and 16.0000 (IQR = 10.0000).
Quartile tip:
IQR helps identify spread in the middle 50% and is robust against extreme outliers compared with full range.
Outputs
Q1, Q2 (Median), Q3
Formula
IQR = Q3 - Q1
Options
Inclusive / Exclusive
Data: 3, 5, 7, 8, 12, 13, 14, 18, 21
Quartiles
6.00 / 12.00 / 16.00
IQR
10.00
The calculator sorts input values and computes median-based quartiles. It then derives IQR to summarize spread in the central half of the data, which is especially useful for skewed datasets.
Q1 = 25th percentileQ2 = medianQ3 = 75th percentileIQR = Q3 - Q1The interquartile range is robust against extreme outliers and is commonly used in box-plot and exploratory analysis.
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