Quartiles Calculator
Compute Q1, Q2, Q3 from a dataset using the percentile interpolation method.
About Quartiles Calculator
Quartiles divide an ordered dataset into four equal parts. Q1 is the 25th percentile, Q2 the 50th (median), and Q3 the 75th percentile. This calculator uses the linear interpolation method (R-7).
Formula
Qk at position p = (k/4)(n−1), interpolate between floor(p) and ceil(p)
- k
- Quartile number (1–3)
- n
- Sample size
- p
- Position index
Worked example
With the default values below, Quartiles Calculator returns Q1 (25th percentile) of 20.2500. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Data (comma separated)
- 7, 15, 36, 39, 40, 41
Results
- Q1 (25th percentile)
- 20.2500
- Q2 (Median)
- 37.5000
- Q3 (75th percentile)
- 39.7500
Step by step
- 1Values used
- 2Formula applied
- 3Q1 (25th percentile)= 20.2500
- 4Q2 (Median)= 37.5000
- 5Q3 (75th percentile)= 39.7500
Assumptions and limits
- The result is derived only from the single input listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What method is used to compute quartiles?
This calculator uses the inclusive (R-7) percentile method with linear interpolation, which matches Excel's QUARTILE.INC function.
How do quartiles relate to percentiles?
Q1 = 25th percentile, Q2 = 50th percentile (the median), and Q3 = 75th percentile. They split the sorted data into four equal-sized groups.