Statistics & Probability

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Third Quartile Calculator.

Calculate this statistic instantly with validated formulas.

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Result: Third quartile (Q3): 6.25000000

Result

Third quartile (Q3): 6.25000000

Use Cases

Analyze test scores

Find the score that separates the top 25% of students from the rest, helping to identify high performers.

Example: Scores: 55, 62, 67, 71, 78, 84, 90 → Q3 = 84

Evaluate income distribution

Determine the income level below which 75% of a population falls, useful for economic analysis.

Example: Incomes: 30k, 45k, 52k, 60k, 75k, 95k → Q3 = 75k

Frequently Asked Questions

What is the third quartile (Q3)?
The third quartile, or 75th percentile, is the value below which 75% of the data falls. It divides your dataset into a lower 75% and an upper 25%.
How does the calculator compute Q3?
It sorts your values and uses linear interpolation between the data points that surround the 75th percentile position, giving a precise estimate even when the position is not an integer.
What does 'linearly interpolated' mean?
When the 75th percentile position falls between two data points, the calculator estimates a value proportionally between them, rather than simply picking the nearest data point.

Tips & Common Mistakes

Tips

  • Enter values separated by commas or spaces, e.g., 1, 5, 7, 9 or 1 5 7 9.
  • Ensure your dataset has at least two values for a meaningful quartile calculation.
  • Use Q3 along with Q1 to compute the interquartile range (IQR) for outlier detection.

Common Mistakes to Avoid

  • Including non-numeric characters like letters or symbols, which cause errors.
  • Using a mix of commas and spaces without proper separation, leading to misreading.
  • Forgetting to sort the data – the calculator sorts automatically, but entering unsorted data is fine.

Last updated: August 13, 2026