Picking the Best PPC Call-to-Action

Picking winning PPC ads seems like an easy task. You find the one ad with the best metric(s) such as conversion rate, pause the rest, spin out a variation of that ad, and test again. This can lead you in the right direction fast, or it sometimes can blind you to another value of your ads, gross conversions.

Below are three case studies that use a metric call Conversion per Impression. The set up for all three case studies is the same. We are picking the wining call-to-action based on a keyword or phrase’s impact on conversion per 100,000 impressions compared to the account average over the past 6 months. Why on this metric and now CTR, or conversion rate, or even CPL/CPA?

PPC Metrics: Conversions per Impression(s)

This metric gives the best indicator of how an ad’s CTR and CR impact the gross number of leads or sales. CTR and CR alone paint an incomplete picture, and CPL is too heavily based on bids. By this I mean that if an ad group with one type of ad has high bids because the keywords in that ad group have high ROAS, then the CPL may be high and thus the ads look like they aren’t worth testing across other ad groups. But in reality, they may produce the most leads per impression! This means that in lower priced ad groups those ads could perform at very low CPL’s.

To calculate your conversions per impression for ads you take a sample number of impressions, for the examples below I use 100,000, and you multiply that number by the CTR of the ads you want to compare. That will give you a clicks number that you then multiply by the conversion rate, which gives you the number of conversions you would get for every 100,000 impressions. The sample set of impressions could be any number you choose, as long as you use the same number to compare your ads. I chose 100,000 because the output was a more tangible and thus easier to compare. (As opposed to doing conversion per 1 impression that would have only been .000071 for the account average in case study 3 below.)

In the below case studies, which were pulled from three random clients, we compare the conversions per 100,000 impressions for the top performing ads compared to the account averages. Keep in mind that some of these have Display campaigns grouped together with Search so CTR is going to look pretty low. Because the ads were tested evenly across Search and Display, the numbers are relative though, so the resulting numbers are comparable.

It is also interesting to note that those ads with the highest conversion rates end up all having the highest conversion per impression numbers. It’s the ads in the #2 spot and below where the difference appears to be made. This is especially important for testing because you may identify call-to-actions that you had written off because of low conversion rate but that deserve a second chance with a new approach.