How to Create a Month Parameter in Tableau

Building a dashboard in Tableau that lets your team instantly switch views between different months can feel like giving them a superpower. Suddenly, they can explore sales trends, marketing performance, or operational data without having to fiddle with clunky filters. This article will show you exactly how to create and use a month parameter to make your dashboards dynamic and much more user-friendly.

What is a Parameter in Tableau and Why Use One for Months?

In simple terms, a parameter is a user-controlled variable that you can build into your Tableau workbooks. Think of it as a dropdown menu, slider, or text box that allows anyone viewing the dashboard to input a value. That value can then be used in your calculations, filters, and reference lines. Standard filters are great, but they are directly tied to a field in your data source. Parameters are more flexible because they aren't tied to any specific field until you tell them to be.

Creating a month parameter gives your audience direct control over the narrative of the data. Instead of presenting a static report for 'last month,' you empower them to ask and answer their own questions, like:

• "How did our sales in March compare to what we saw in April?"
• "What was our website traffic in October when we ran that big campaign?"
• "Can I quickly see the support ticket volume for each month this year?"

This interactivity transforms a static report into an exploratory tool, making your dashboards significantly more valuable.

Getting Your Data Ready for a Month Parameter

Before you build the parameter, it's essential to ensure your data is set up correctly. For Tableau to understand months, it needs a valid date field to work from. In your Data Source tab or in the Data pane, find the column that contains your dates (e.g., 'Order Date', 'Sign Up Date', 'Transaction Date').

Hover over the icon next to the field name. It should be a small calendar icon, which indicates it's a 'Date' or 'Date & Time' data type.

If you see 'Abc' (string) or '#' (number), Tableau won't be able to extract the month names properly. To fix this, simply click on the icon and change the data type to Date. Once your date field is correctly formatted, you are ready to build the parameter.

Step-by-Step: How to Create and Use a Month Parameter

Creating and implementing a month parameter involves a few key steps: creating the parameter itself, linking it to your data with a calculated field, and then applying that calculation as a filter. Let's walk through it with a common example: filtering sales data by month.

Step 1: Create the Month Parameter

First, you need to create the dropdown list of months that your users will interact with.

1. In the Data pane on the left, right-click on any empty space and select Create Parameter... A new configuration window will open.
2. Name It: Give your parameter an intuitive name. Something like "Select a Month" works well because it clearly communicates the action to the user.
3. Set the Data type: For month names, change the 'Data type' to String. This will allow you to use text values like "January," "February," etc.
4. Set the Allowable values: Change this to List. This lets you define the specific values that will appear in your dropdown menu.
5. Add the Months to Your List: Under 'List of values,' click in the left 'Value' column and type in each month's name. You can simply list all twelve months:
6. Click OK. You'll now see your new parameter listed at the bottom of the Data pane under a "Parameters" section.

Your parameter is created, but it doesn't do anything yet. It's just a variable waiting for instructions.

Step 2: Show the Parameter Control

Now, let's make the parameter visible on your worksheet so you can interact with it.

• Right-click on your newly created "Select a Month" parameter in the Data pane and choose Show Parameter. A dropdown menu or list will appear, usually in the top right corner of your view, showing the list of months you just created.
• You can click on this dropdown and select different months, but you'll notice it still doesn't affect your visualization. That's because we haven't told Tableau how this parameter should relate to our data. We'll do that in the next step.

Step 3: Create the Calculated Field to Connect the Parameter

This is where the magic happens. We need to create a simple calculation that tells Tableau which data to show based on the month selected in the parameter. This calculation will act as our dynamic filter.

1. Right-click on an empty space in the Data pane and select Create Calculated Field...
2. Give the calculated field a clear name, such as "Month Filter" or "Selected Month Logic."
3. In the formula box, enter the following calculation, replacing [Order Date] with your own date field:

DATENAME('month', [Order Date]) = [Select a Month]

Let's break down this formula:

• DATENAME('month', [Order Date]): This function looks at your [Order Date] field and extracts the full name of the month (e.g., "January", "February") as a string.
• =: This is a simple comparison operator.
• [Select a Month]: This references our parameter. It represents whatever value is currently selected in the dropdown menu.

The entire formula asks a true/false question for every row in your data: Does the month name in this row match the month selected in the parameter? The result will be either True or False.

Click OK to save the calculated field.

Step 4: Apply the Calculation as a Filter

The final step is to use this new True/False calculation to filter your view.

1. Find your "Month Filter" calculated field in the Data pane.
2. Drag it onto the Filters shelf.
3. A dialog box will appear asking you which values to filter for. You will see options for 'True', 'False', and often 'Null'.
4. Check the box for True and click OK.

And that's it! Your visualization will now instantly update based on the month you select in the "Select a Month" parameter control. By filtering for 'True', you've told Tableau to only show data where the month name in your data source matches the user's selection.

Advanced Tips and Tricks with Month Parameters

Once you are comfortable with the basics, you can use parameters to create even more powerful and intuitive dashboards.

Dynamically Update Your Chart Title

A static title like "Monthly Sales Report" isn't very helpful when the view is changing. You can make your title dynamic by including the parameter.

1. Double-click the title of your worksheet to edit it.
2. Type your title, and where you want the month to appear, click the Insert button.
3. From the dropdown, select your [Select a Month] parameter.
4. Click OK.

Now your title will read something like "Sales Performance for March" and will automatically update whenever a user chooses a new month.

Using a Number-Based Month Parameter

While using month names ("String") is user-friendly, sometimes using numbers for months (1 for January, 12 for December) can be better for certain calculations.

The setup is similar:

1. Create a parameter with the Integer data type.
2. Under 'Allowable values', choose List. In the 'Value' column, enter 1, 2, 3... and in the 'Display As' column, enter "January", "February", "March..." This shows the user the name but stores the value as a number.
3. Your calculated field formula then uses DATEPART instead of DATENAME:

DATEPART('month', [Order Date]) = [Select Month Number]

This method can be useful when you need to perform mathematical operations based on the month, such as calculating year-to-date totals or comparing with the previous month.

Final Thoughts

Mastering parameters in Tableau is a simple way to drastically improve the functionality and add a professional touch to your reports. By creating a month parameter, you replace static, one-off analyses with an interactive, exploratory experience that empowers your team to dig into the data themselves.

While building dashboards in Tableau is a powerful skill, sometimes the goal is to get insights without spending time on setup and configuration. We created Graphed to do exactly that. You can connect your marketing and sales data sources in seconds, and instead of building calculated fields and parameters, you can just ask in plain English: "Show me a chart of our Shopify revenue each month this year" or "compare Facebook Ads CPA for March vs April." Graphed instantly builds the visual for you, turning hours of report building into a 30-second conversation with your data.