How To Find Q1 In Excel

The first quartile, often denoted as Q1, is a measure of the lower 25 % of a data set. In Excel, you can find Q1 with built‑in functions, array formulas, or by using PivotTables, each offering a different balance of flexibility and ease of use. This guide walks you through every common method, explains the underlying mathematics, and provides tips for troubleshooting typical pitfalls Simple, but easy to overlook. And it works..

Understanding Quartiles

Before diving into Excel commands, it helps to know what a quartile represents. Quartiles divide a sorted data set into four equal parts:

• Q1 – the 25th percentile, separating the lowest 25 % of observations.
• Q2 – the median, or 50th percentile.
• Q3 – the 75th percentile.

Excel offers two families of functions for quartiles: QUARTILE.In practice, iNC and QUARTILE. EXC, each with a different way of handling the data range.

Method 1: Using the QUARTILE.INC Function

The QUARTILE.INC function returns the quartile using an inclusive method, meaning it includes the endpoints of the data range. The syntax is:

QUARTILE.INC(array, quart)

• array – the range of cells containing your numeric data.
• quart – the quartile you want (0 for minimum, 1 for Q1, 2 for Q2, 3 for Q3, 4 for maximum).

Example

Assume your data is in cells A2:A31. To compute Q1:

=QUARTILE.INC(A2:A31, 1)

This formula will return the value that marks the 25th percentile of the range, treating the smallest and largest values as part of the data set.

Method 2: Using the QUARTILE.EXC Function

The QUARTILE.EXC function uses an exclusive method, which excludes the endpoints. It is often preferred when you want to compute quartiles in a way that matches the textbook definition Simple, but easy to overlook..

Syntax:

QUARTILE.EXC(array, quart)

Example

=QUARTILE.EXC(A2:A31, 1)

The result may differ slightly from QUARTILE.INC, especially when the data set is small or contains outliers.

Method 3: Using PERCENTILE.INC and PERCENTILE.EXC

Because Q1 is the 25th percentile, you can also use the percentile functions:

• PERCENTILE.INC – inclusive version.
• PERCENTILE.EXC – exclusive version.

Syntax

PERCENTILE.INC(array, k)
PERCENTILE.EXC(array, k)

where k is the percentile expressed as a decimal (0.25 for Q1).

Example

=PERCENTILE.INC(A2:A31, 0.25)

or

=PERCENTILE.EXC(A2:A31, 0.25)

These formulas are interchangeable with the quartile functions for the 25th percentile, but they can also be used for any other percentile.

Method 4: Manual Calculation with Sorting and Indexing

If you prefer a hands‑on approach, you can sort the data and locate Q1 manually:

1. Sort the range in ascending order Still holds up..

2. Determine the position of Q1 using the formula:

   • For inclusive quartiles: position = (n + 1) * 0.25
   • For exclusive quartiles: position = (n - 1) * 0.25

   where n is the number of observations.

3. If the position is an integer, take the value at that index. If it is fractional, interpolate between the two nearest values.

Example

With 30 values, the inclusive position is (30 + 1) * 0.75. On top of that, 25 = 7. You would take the value at the 7th position and add 0.75 times the difference between the 8th and 7th values.

Method 5: Using a PivotTable

PivotTables provide a quick visual summary and can display Q1 without writing formulas:

1. Select your data range.
2. Insert a PivotTable.
3. Drag the field you want to analyze to the Values area.
4. Click the field, choose Value Field Settings, then select Quartile (or Percentile) and specify 1 for Q1.
5. The PivotTable will show the Q1 value in the summary.

Method 6: Leveraging Power Query

For large data sets or repeated transformations, Power Query (Get & Transform) can compute quartiles:

1. Select the data, then Data → Get & Transform → From Table/Range.