Why CPA isn’t the only metric that matters in paid media

Are we too focused on the final conversion?

CPA is one of the most commonly used metrics in paid media. And for good reason. If the objective is to generate conversions, understanding how much we're paying for each one is incredibly valuable.

The problem comes when we start treating CPA as the ultimate measure of success for every campaign. Not every campaign is designed to drive an immediate conversion. And not every customer journey starts with someone searching for a product and clicking ‘buy’. People might see a brand on social media, watch a video, visit the website a few days later, search for the brand, and eventually convert. If we only look at the CPA attached to that final conversion, we're potentially ignoring everything that happened before it.

Different objectives need different measures

One of the biggest things I've learnt from working across paid social is that the metric you use to judge a campaign should reflect what the campaign is actually trying to achieve. For a conversion campaign, CPA might be one of the most important metrics to monitor. But for an awareness campaign, I wouldn't expect CPA to tell me very much.

Instead, I'd be looking at metrics such as:

• Reach and impressions

• Video views and completion rates

• Engagement

• Cost per engagement

• Click-through rate

• Website traffic

• Brand searches

• New users

These metrics help us understand whether we're successfully getting a brand in front of the right people and creating interest. That doesn't mean conversions aren't important. It means we need to understand where that campaign sits within the wider customer journey.

The customer journey isn't linear

This is where I think paid media reporting can sometimes become too simplistic.

We like being able to say:

£500 spend → 50 conversions → £10 CPA.

It's easy to understand, easy to report and easy to compare. But the reality is rarely that straightforward. A customer might first discover a brand through a TikTok video. They might then see an Instagram ad, visit the website, leave without purchasing, and come back through Google Search two weeks later.

Which channel gets the credit?

If we're relying heavily on last-click attribution, Google Search might get the conversion. But that doesn't necessarily mean it was responsible for creating the demand in the first place. This is why looking at individual channel performance in isolation can give us an incomplete picture.

So, should we stop looking at CPA?

Absolutely not. CPA is still a hugely important metric.

If I'm running a conversion-focused campaign, I want to know whether we're acquiring customers efficiently. If CPA is increasing significantly, that's something I need to investigate. The issue is when we use the same measurement framework for every stage of the funnel. Someone who has never heard of a brand before is very different from someone who has already visited the website three times and added a product to their basket. We shouldn't necessarily expect them to have the same value or behave in the same way.

The job of the marketer is to understand that difference.

What should we measure instead?

For me, the answer isn't to replace CPA with one new ‘perfect’ metric. It's about looking at a combination of metrics that tells the full story.

For example:

Awareness: Are we reaching the right people and getting their attention?

Consideration: Are people engaging with the content, visiting the website and showing an interest in the brand?

Conversion: Are those people ultimately taking the action we want?

Retention: Are we generating customers who come back and continue to buy? Each stage has a different job, so it makes sense that each stage should have different KPIs.

The bigger picture

The more channels and touchpoints we add to a marketing strategy, the harder it becomes to attribute a conversion to one specific interaction. That's not a reason to stop measuring. It's a reason to measure more intelligently. I think the most useful reporting doesn't simply tell you what happened. It should help explain why it happened, what role each activity played and what we should do next.

A campaign with a higher CPA isn't automatically a bad campaign. Equally, a campaign with a great CPA isn't automatically the best campaign. We need to understand the objective, the audience, the stage of the funnel and the wider customer journey before deciding whether something has been successful.

CPA is a useful metric. But it's only one piece of the puzzle. And in paid media, sometimes the most valuable activity is happening well before the conversion that eventually gets counted.

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