Target CPA, explained properly.
What is Target CPA?
Target CPA (Target Cost Per Acquisition) is a Google Ads [Smart Bidding](/ppc-glossary/smart-bidding) strategy. You tell Google what you want to pay per conversion, and it automatically sets bids in every auction to achieve as many conversions as possible at or below that target. It is like having a procurement target. You set a maximum spend per lead and Google works out the optimal bid for every single search.
How Target CPA works
Google uses historical conversion data alongside dozens of real-time signals to predict the conversion probability of each click. It then bids what it calculates will deliver a conversion at your target cost. You set a target cost per acquisition (for example, 40 pounds per lead). Google's machine learning then sets each individual bid in real time, factoring in: - The user's likelihood to convert based on signals like device, location, time of day, and previous behaviour. - The competitiveness of the auction at that moment. - Historical conversion data from your account. Google aims to keep the average CPA across all conversions at or below your target, while still spending the available budget. Some conversions will cost more, others less; the average is what you set.
Setting the right target
Setting too aggressive a target can starve the campaign of volume, because Google becomes too selective and misses viable conversions. The best starting point is your current actual CPA from historical data, then tighten gradually.
When Target CPA works best
Three conditions need to be true for Target CPA to outperform alternatives: 1. **Reliable conversion tracking.** Smart Bidding is only as good as the data feeding it. Inaccurate or missing conversion data produces worse-than-manual results. 2. **Sufficient conversion volume.** Google recommends at least 30 conversions in the previous 30 days. Below that, the algorithm cannot find a stable pattern. 3. **A realistic target.** Set a target that is achievable based on past performance. Setting a target dramatically below your historic CPA usually causes the campaign to under-deliver as Google struggles to find conversions at the unrealistic price. It also works best with stable, consistent conversion actions such as form fills or calls, and at least 2 to 4 weeks of clean conversion history before enabling. Our [PPC service](/services/ppc-packages) monitors Target CPA campaigns closely, setting realistic targets based on actual account data and adjusting them gradually rather than making big jumps that trigger the learning period.
Target CPA vs Maximise Conversions
Maximise Conversions tries to get as many conversions as possible within budget, regardless of CPA. Target CPA enforces an average price ceiling. The choice depends on what matters more: hitting a fixed CPA (Target CPA) or maximising volume even if CPA fluctuates (Maximise Conversions).
Take this further
Target CPA is one of the cleanest ways to align Google Ads spend with actual business outcomes. Most accounts that have steady conversion volume see better results from Target CPA than from manual bidding. Ready to apply this to your own account? [Book a free discovery call](/discovery-call), or explore our [PPC packages](/services/ppc-packages).
Target CPA: common questions.
How do I set the right Target CPA?
Look at your historic CPA across the last 30 to 60 days under your previous bidding strategy. Start with a Target CPA close to that historic average; once Smart Bidding stabilises (after two to four weeks), gradually push it down 10 to 15 per cent at a time to find your floor.
How long does Target CPA take to learn?
Two to four weeks typically. During this learning phase, performance can swing as the algorithm tests different bid combinations. Avoid making changes during this period unless something is clearly broken.
Why is Target CPA not getting any conversions?
The most common cause is that the target is too low compared to the auction's reality, so Google cannot find enough opportunities at that price. Other causes are insufficient conversion data (fewer than 30 conversions per month), broken conversion tracking, or recent account changes that reset learning.
Can I change Target CPA without resetting learning?
Yes, small adjustments (10 to 15 per cent) are fine and rarely reset learning. Large changes (50 per cent or more) can effectively reset the algorithm because the new target represents a different optimisation problem. Adjust gradually.
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