How to Add Two Columns in Tableau

Adding two columns together is a fundamental task in data analysis, allowing you to create new metrics and dimensions from your existing data. In Tableau, this is most often done by creating a calculated field. This article will walk you through exactly how to add both numeric and text columns, handle common issues like null values, and apply aggregations correctly.

Why Would You Need to Add Columns in Tableau?

Before jumping into the how-to, let's quickly cover a few scenarios where adding columns is a necessary step. It's a common data preparation task that unlocks deeper insights.

• Creating New Metrics: You might want to combine Sales and Shipping Fees to get a Total Order Value. Or maybe add Product Cost and Marketing Cost to understand the total investment per item.
• Combining Text Fields: A classic example is combining a First Name column and a Last Name column to create a Full Name field. This makes labels on charts and tables much cleaner.
• Calculating Custom KPIs: While not always simple addition, many key performance indicators (KPIs) start by combining multiple fields. For example, understanding total variable costs might involve adding Material Costs, Labor Costs, and Shipping Costs.

Essentially, adding columns allows you to create a more complete and analysis-ready dataset directly within Tableau, without having to go back to your original spreadsheet or database.

How to Add Two Numeric Columns Using a Calculated Field

The most direct way to sum two columns is by creating a calculated field. This generates a new column (a "field" in Tableau terminology) in your data pane that you can use just like any of your original columns.

Let’s use a common e-commerce example. Imagine you have a dataset with columns for [Sales] and [Shipping Cost]. You want to create a new column called Total Price that is the sum of these two.

Step 1: Open the Calculated Field Editor

First, navigate to the Data pane on the left side of your Tableau worksheet. You'll see your list of dimensions and measures.

Click the small downward-facing arrow at the very top of the Data pane. From the dropdown menu, select Create Calculated Field…

Alternatively, you can right-click anywhere in the empty space of the Data pane and select the same option.

Step 2: Name Your New Field

A dialog box will pop up. The first thing you should do is give your new field a descriptive name. In this case, we'll type Total Price into the name box at the top.

Step 3: Write the Addition Formula

This is where the magic happens. In the large text area of the dialog box, you'll write the formula to add your columns. The syntax is straightforward: you reference your column names and place a plus sign (+) between them.

To add the Sales and Shipping Cost columns, your formula will be:

[Sales] + [Shipping Cost]

As you start typing, Tableau's autocomplete feature will suggest field names from your data source. You can select [Sales], and as you continue typing, it will help prevent typos in your field names, which is a common cause of errors. At the bottom of the dialog box, you'll see "The calculation is valid." If there's an error, Tableau will tell you what's wrong so you can fix it.

Step 4: Save and Use Your New Field

Click OK to save your calculated field. You will now see Total Price appear in your Data pane under the Measures section (since it’s a number). It will have a small sign that indicates it's a calculated field.

Now you can use this Total Price field just as you'd use either column. Drag it onto the Rows or Columns shelf, drop it onto the Marks card to add color or as a label, or use it in other calculations. Tableau automatically summarizes all values, giving you a SUM[Total Price] pill.

Adding Text Columns (Concatenation)

Sometimes, adding means joining two string fields instead of calculating their sum. This is called concatenation. For example, you want to combine a First Name column with a Last Name column to get a Full Name.

Step 1: Create a Calculated Field

Repeat the Step 1 from the previous section to open the Calculated Field editor. Name your field Full Name.

Step 2: Write the Concatenation Formula

Your formula will include a + sign to join the two names. To accomplish this, you simply add a space character enclosed in quotes between the two names.

[First Name] + " " + [Last Name]

Without the space, your resulting field would be JohnSmith, which is not ideal. By adding the space, you create a readable name like "John Smith".

Dealing with Common Problems

When creating calculated fields, you may encounter null values in columns. To deal with this, you can use functions like ZN() to convert nulls to zero for numerical calculations.

A Quick Note on Aggregation

When you place calculations in your Tableau view, you’ll notice that Tableau automatically wraps your field with an aggregation, like SUM(), AVG(), or MIN(). The formula we wrote earlier, [Sales] + [Shipping Cost], is a row-level calculation. This means the calculation is performed for every single row in your data source before any aggregation happens.

In most cases, this is exactly what you want. You want to calculate the Total Price for each individual order first, and then sum up all the total prices later to get the grand total.

However, you can also perform the calculation at an aggregate level. The formula would look like this:

SUM([Sales]) + SUM([Shipping Cost])

The result is often the same, but the order of operations is different. Here, Tableau first sums up all the values in the [Sales] column, then sums up all the values in the [Shipping Cost] column, and then adds those two grand totals together. For simple addition, both methods work, but understanding the difference between row-level and aggregate calculations is vital as your formulas become more complex.

Final Thoughts

Knowing how to add columns via calculated fields is a foundational skill in Tableau. Whether you're summing numeric data to create new performance indicators or concatenating text fields for clearer labels, the process remains simple and consistent. By also learning how to handle potential issues like null values with the ZN() function, you can ensure your analyses are always accurate and reliable.

While the calculated field editor in Tableau is powerful, it does come with a learning curve. We created Graphed because we believe getting insights from your data shouldn't require you to learn special syntax or memorize function names. You can just connect your data sources - like Shopify, Google Analytics, or Salesforce - and ask questions in plain English, like "Show me a chart of total sales plus shipping costs over the last quarter." We handle the logic and build the visuals instantly, turning hours of report building into a 30-second conversation.