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Interquartile range (IQR) calculator

Compute the first quartile, third quartile and interquartile range of a dataset.

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Need Q1 (25th percentile), Q3 (75th percentile), Interquartile range? The Interquartile range (IQR) calculator derives it from Numbers (comma-separated) in one step. For instance, with Numbers (comma-separated) = 2, 5, 7, 8, 10, 13, 18, 21, 25, 30 it returns Q1 (25th percentile) = 7.25, Q3 (75th percentile) = 20.25 and Interquartile range = 13.

How to use it

  1. Enter your values: Numbers (comma-separated).
  2. Read the result instantly: Q1 (25th percentile), Q3 (75th percentile), Interquartile range.

Frequently asked questions

What does the Interquartile range (IQR) calculator actually compute?

It takes Numbers (comma-separated) and derives Q1 (25th percentile), Q3 (75th percentile) and Interquartile range from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

A single value: Numbers (comma-separated). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Numbers (comma-separated) = 2, 5, 7, 8, 10, 13, 18, 21, 25, 30, the calculator returns Q1 (25th percentile) = 7.25, Q3 (75th percentile) = 20.25 and Interquartile range = 13. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Numbers (comma-separated) = 2, 5, 8, 9, 12, 16, 23, 28, 35, 44 instead, Q1 (25th percentile) goes from 7.25 to 8.25 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Numbers (comma-separated) = 2, 5, 7, 8, 10, Q1 (25th percentile) comes out at 5. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Summarising a dataset before drawing conclusions from it, checking whether a difference between two groups is real, and putting an interval around an estimate.

What is the most common mistake?

Reading a p-value as the probability that the hypothesis is wrong. It is the probability of seeing data at least this extreme if the null were true — a different statement, and a much weaker one.

What is the difference between the Interquartile range (IQR) calculator and the Outlier detector (IQR method)?

This one returns Q1 (25th percentile) and Q3 (75th percentile); the Outlier detector (IQR method) returns Lower bound and Upper bound. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Range calculator is the closest one after this: Find the range, minimum and maximum of a list of numbers.

What else is worth having open alongside it?

Coefficient of variation calculator and Correlation coefficient calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
ExplainerGeometric vs Arithmetic Mean: Which to UseThe arithmetic mean adds and divides; the geometric mean multiplies and takes a root. Learn which fits growth rates, ratios, and averages.ExplainerWhat Is a Percentile? The 90th Percentile ExplainedA percentile tells you where a value ranks within a group. Learn what the 90th percentile really means and why a percentile is not the same as a percentage.How-toHow to Calculate a Weighted AverageA weighted average gives some values more influence than others. Learn the Σ(w·x) / Σw formula with grade and portfolio examples you can follow step by step.How-toHow to Find a Cube Root by HandA step-by-step guide to finding a cube root by estimation and refinement — plus how it differs from a square root and when a value stays irrational.ExplainerHow Exponents Work: Powers and the Laws of ExponentsAn exponent is repeated multiplication. Learn the laws of exponents, what negative and fractional powers mean, and why anything to the zero is one.How-toHow to Calculate Percent Error: The Accuracy Formula for SciencePercent error tells you how close a measurement is to the true value. Learn the formula, work through an example, and see how scientists use it to judge accuracy.