Use Custom Columns in Google AdWords? Beware of Incorrect Calculations

Custom Columns is a cool feature in Google AdWords that lets you create your own columns in the AdWords web interface.

For example, you can change the name of “Conversions” to “Orders” and “Cost per Conversion” to “CPO” if you’re an e-tailer.

But you can also use Custom Columns to calculate custom metrics and KPIs.

For example, we have a client who uses a metric called "A/S Ratio" instead of "ROAS." Rather than looking at the amount of revenue created from every dollar spent (Revenue divided by Cost), they do the inverse: the amount of cost as a percentage of revenue (Cost divided by Revenue).

Without Custom Columns, all reporting would need to be customized outside of AdWords before delivery to the client. And, when optimizing, account managers would need to frequently calculate the A/S equivalent of each ROAS number they see in AdWords.

That makes managing an account at scale challenging and is a perfect use-case for Custom Columns.


How To Create Custom Columns In AdWords

Here’s how to create a custom column for the metric “A/S Ratio” (calculated as cost divided by revenue, expressed as a percentage):

1. On the Campaigns or Ad Groups tabs, click the Columns button and click Modify columns.



2. Click on Custom columns and then the red +Column button.



3. Name your custom column.



4. Begin building your formula by clicking Select a metric, then Performance, then Cost.



5. Click the division symbol.



6. Click Select a metric, click Conversions, then click All conv. value.



7. In the drop-down box, change Currency ($) to Percent (%).



8. Click Save, then add your new custom column to the list of fields to display.



9. Your columns should now look like this: 



We recommend that you carefully check your new Custom Column to ensure it’s calculating correctly!


How To Separate Leads from Purchases In Columns

Another big red flag to be aware of is that calculated metrics based on segmented data tend to be wildly incorrect. Let’s work through an example to show you what we mean here.

One of our clients has two key types of conversions: Leads and Purchases. Leads are defined as someone fills out a form on their website and provides their name and email address.

The client has many different types of lead conversions. For example, whitepaper downloads, webinar registrations, free trial sign-ups, etc. Each of those has its own conversion pixel in AdWords.

The client came to us and said they wanted an easy way to group all the various lead conversions into one column and the purchase conversion into another.

Easy to do with Custom Columns.

First, we create a new column titled Leads. In the Formula section, click Select a metric, then Conversions. Click on Conversions again top open up the segmentations, then click on Conversion name. Now you will see a list of all the various conversion actions in your account.

conversion segmentation.png


Click on the ones you want to include -- in this case, all the different conversion actions that represent leads to this client -- and you see them populate to the Selected segments column.

Once you have them all selected, click Save. Repeat the above steps for your Purchase conversion too. Now, on the campaign and ad group tabs, you can have separate columns for totaling up Leads and Purchases.


Beware of Calculated Metrics Using Segmented Data

If you also want to include some calculated metrics, like Cost per Lead (“CPL”), that’s where we see Custom Columns start to falter.

In theory, you would follow the above steps, first adding Cost to your formula, then a divide symbol, then Conversions. You would segment only the conversion actions that represent Leads. This method should tell us the CPL, or Cost per Lead.

In our testing, however, there appears to be a bug in the Custom Columns product that renders these calculations incorrect by a factor of 10X or more, making them worthless.


Limitations With Custom Columns In Google AdWords

Long story short, Custom Columns are great for calculating your own custom KPIs. They're also ideal for segmenting some of your data into a new column. But they are not yet capable of calculating your own custom KPIs using segmented data.

One final limitation to keep in mind is that they're only available on the Campaigns and Ad Groups tabs. To be truly useful, Google needs to roll the feature out to every tab of the AdWords web app, and we suspect (hope) that will happen soon enough.

Use the form below to let us know if you have any questions about Custom Columns that we didn’t cover here.