Which quartile method does this use?

This tool uses the exclusive (Tukey/Mendenhall) method: Q2 is the true middle value, and Q1/Q3 are medians of the strict lower and upper halves (excluding Q2 when n is odd). This is the most common method taught in introductory statistics.

What is the IQR used for?

The interquartile range measures the spread of the middle 50% of your data. It is resistant to outliers and is used to build box plots and to detect outliers via the fence rule: any value below Q1 − 1.5×IQR or above Q3 + 1.5×IQR is flagged as an outlier.

What is the minimum dataset size?

You need at least 4 values to compute meaningful quartiles. Fewer values will yield a result, but it may not be statistically meaningful.

Does the tool handle decimals and negative numbers?

Yes. Any valid number — including negative values, decimals, and integers — is accepted. The tool sorts them numerically before computing quartiles.

What is the five-number summary?

The five-number summary consists of: minimum, Q1, Q2 (median), Q3, and maximum. Together they give a compact description of a dataset's distribution and are the basis for box-and-whisker plots.

Quartile Calculator

Name: Quartile Calculator
Availability: InStock
Author: Nham Vu

Enter a list of numbers to instantly calculate Q1, Q2 (median), Q3, IQR, and the five-number summary.

Dataset

Enter numbers separated by commas, spaces, or new lines.

Enter numbers on the left and press Calculate.

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Summary

Enter a list of numbers to instantly calculate Q1, Q2 (median), Q3, IQR, and the five-number summary.

How it works

Enter your numbers separated by commas, spaces, or newlines.
The tool sorts the dataset in ascending order.
Q2 (median) is the middle value of the sorted set.
Q1 is the median of the lower half (values below Q2).
Q3 is the median of the upper half (values above Q2).
IQR is calculated as Q3 minus Q1.

Use cases

Summarize a dataset for a statistics assignment or report.
Identify outliers using the IQR fence method (Q1 − 1.5×IQR, Q3 + 1.5×IQR).
Prepare a five-number summary for a box-and-whisker plot.
Analyze score distributions for exams or surveys.
Measure data spread and skewness in finance or research.
Verify hand-calculated quartiles for homework or review.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu