Quartile Calculator
Enter numbers separated by commas, spaces or line breaks to calculate Q1, median (Q2), Q3 and the interquartile range.
How to Use the Quartile Calculator
Enter numerical data to calculate the lower quartile, median and upper quartile.
Practical Example
For 1, 2, 3, 4, 5, 6, 7, 8, the median lies between 4 and 5 while Q1 and Q3 summarize the lower and upper halves.
Factors That Affect the Result
Sorting, sample size and the quartile convention used can cause small differences between methods.
Frequently Asked Questions
What is Q1?
Q1 is the lower quartile, near the 25th percentile.
What is Q3?
Q3 is the upper quartile, near the 75th percentile.
Why can calculators show different quartiles?
Several accepted interpolation and median-splitting methods exist.
Understanding Quartiles and IQR
Quartiles divide ordered data into four parts. Q2 is the median, while Q1 describes the lower half and Q3 the upper half. The interquartile range is IQR = Q3 − Q1 and measures the spread of the middle 50% of observations.
Why Results Can Vary
Different statistical conventions calculate Q1 and Q3 slightly differently, especially for small samples. A spreadsheet, textbook, and calculator can therefore produce different quartile values without either being inherently wrong. Use one method consistently when comparing data sets or reproducing an analysis.
IQR is resistant to extreme values and is commonly used in box plots and outlier rules. A typical exploratory rule flags values below Q1 − 1.5×IQR or above Q3 + 1.5×IQR, but such points are not automatically errors and should be interpreted in context.