🧮 Quartile Calculator
Enter your data values (leave extra boxes blank if you have fewer than 10) to calculate the first, second, and third quartiles.
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What Are Quartiles?
Quartiles split a sorted data set into four equal parts. Q1 marks the boundary below which 25% of the data falls, Q2 is the median (50%), and Q3 marks the boundary below which 75% of the data falls.
The Formula
This calculator uses the linear interpolation method: it finds the position (p × (n−1)) for each quartile in the sorted list, then interpolates between the two nearest data points if that position isn’t a whole number. This is the same method used by many spreadsheet programs by default.
- Enter at least one value; leave unused boxes blank.
- The interquartile range (Q3 − Q1) is also shown, describing the spread of the middle half of the data.
Provided for general statistical education and exploratory data analysis.
Last reviewed August 2026