Tableau Aggregations
When you drag a Measure to a chart, Tableau does not just show raw numbers. It groups and summarizes them. This summary is called an aggregation. Understanding aggregations helps you show the right number at the right level.
What Is an Aggregation
An aggregation takes many individual values and produces one summary value. It answers questions like: What is the total? What is the average? What is the highest value?
Classroom Analogy
Student test scores: 72, 85, 90, 68, 77 SUM = 72+85+90+68+77 = 392 (total score across all students) AVG = 392 / 5 = 78.4 (average score per student) MAX = 90 (highest score) MIN = 68 (lowest score) COUNT = 5 (number of students who took the test)
Default Aggregation in Tableau
Every time you drag a Measure to the Rows or Columns shelf, Tableau automatically wraps it in SUM(). You see "SUM(Sales)" on the shelf — not just "Sales." Tableau chooses SUM because adding up values is the most common business need.
How to Change Aggregation
Right-click any Measure on a shelf or in the view. Hover over "Measure (Sum)" in the menu. A submenu appears with all available aggregation options. Click one to switch. The chart updates instantly.
Available Aggregations
| Aggregation | What It Calculates | When to Use It |
|---|---|---|
| SUM | Adds all values | Total sales, total revenue |
| AVG | Calculates the mean | Average order value, average rating |
| COUNT | Counts number of rows | Number of orders, number of customers |
| COUNT (DISTINCT) | Counts unique values only | Number of unique customers (no duplicates) |
| MIN | Finds the smallest value | Earliest date, lowest price |
| MAX | Finds the largest value | Latest date, highest sales order |
| MEDIAN | Finds the middle value | Median income, median delivery time |
| STDEV | Measures how spread out values are | Analyzing variability in sales performance |
Level of Aggregation Depends on Dimensions
The aggregation result changes based on which Dimensions appear in your view. Tableau aggregates the Measure separately for each combination of Dimension values visible on screen.
Diagram: Aggregation Changes with Dimensions
Raw Data: Region | Category | Sales East | Furniture | 500 East | Technology | 800 West | Furniture | 300 West | Technology | 600 View 1 — Dimension: Region only → SUM(Sales) per Region East = 500 + 800 = 1,300 West = 300 + 600 = 900 View 2 — Dimensions: Region + Category → SUM(Sales) per Region + Category East Furniture = 500 East Technology = 800 West Furniture = 300 West Technology = 600
Adding more Dimensions breaks the data into smaller and smaller groups. Removing Dimensions combines groups back into larger totals.
Aggregation vs Row-Level Calculation
Some calculations run on individual rows before any grouping. Others run after grouping (on aggregated results). Tableau separates these two clearly. A row-level calculation might compute "Profit Margin = Profit / Sales" for every single order. An aggregated calculation might compute "AVG(Profit Margin)" across all orders in a region. Trying to mix both in one formula causes an error — Tableau will warn you.
Setting the Default Aggregation for a Field
You can set a permanent default aggregation for any Measure. Right-click the field in the Data Pane, select "Default Properties," then "Aggregation." Choose your preferred aggregation. Every time you drag that field to any view, Tableau uses your chosen aggregation instead of SUM.
Disaggregating Measures
Sometimes you want to see every individual data point without any aggregation — like a scatter plot showing each order as a dot. Go to the Analysis menu and uncheck "Aggregate Measures." Tableau now shows raw row-level values. Each row in your data becomes a separate mark on the chart.
Use Case: Disaggregation
Aggregated (SUM per Region): East = 1 bar at $1,300 Disaggregated (each order as a dot): East = 2 dots at $500 and $800 separately West = 2 dots at $300 and $600 separately
Summary
Aggregations summarize many values into one — SUM adds, AVG averages, COUNT counts, MIN finds smallest, MAX finds largest. Tableau defaults to SUM and updates automatically as you add or remove Dimensions. Change aggregation by right-clicking any Measure on the shelf. Use disaggregation when you need to see every individual data point.