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# Add Custom Column to Table
This guide explains how to add a custom column to an existing table in the dashboard. A **custom column** is a calculated column defined with a formula that uses other columns (e.g. \[Clicks]/\[Impressions]). Custom columns are available in both the table view and any chart that uses the same visualization data (e.g. when you switch the same block to a line or bar chart). Use it when you want metrics like CTR, CPA, ROAS, or any expression built from existing numeric columns without changing the data source.
### Steps to Add Custom Column:
1. **Open visualization settings**
* Click the **Settings** (gear) icon on the table block.
* In the right-hand panel, select the **Chart** tab.
* Scroll below to the **Custom Columns** section.
2. **Add a new column**
* Click **Add Custom Column**.
* From the **Available columns** click a column to insert it into the formula, you can also manually type the column name in the **Formula** within square brackets (e.g. \[clicks]).
* You must name the formula you have generated, inside the **Formula Name** field, this will also appear as the column label.
* Since spaces are not allowed in the formula name, if you want a space to appear in the column label, add an underscore ( ‘\_’ ) between words (e.g. ‘average\_cpm’ will appear as ‘Average Cpm’ on the table).