Target CPA (tCPA)
Target CPA (tCPA) is an automated bidding strategy in which the ad platform sets bids in each auction to generate as many conversions as possible at an average cost per acquisition close to the target the advertiser specifies.
tCPA is a Smart Bidding strategy in Google Ads (and available in similar form in Microsoft Advertising). You tell the platform what you are willing to pay for a conversion — say $40 per lead — and it uses machine learning on signals like device, location, time of day, query, audience and browser to bid higher on auctions likely to convert and lower on the rest. The target is an average, not a cap: some conversions will cost $15 and others $90, and the strategy aims for the mean over time. In current Google Ads interfaces tCPA appears as a Target CPA field inside the Maximize Conversions strategy rather than as a separate option.
Three conditions decide whether it works. First, conversion tracking has to be accurate and reasonably fast — if conversions are imported days later or fire on the wrong events, the model learns from bad data. Second, volume: the practical guidance is roughly 30 or more conversions in the trailing 30 days per campaign, and below that the algorithm has too little signal to beat manual or Maximize Conversions bidding. Third, patience through the learning period, typically one to two weeks or one conversion cycle, during which CPA is volatile and mid-flight edits restart the process.
The most common mistake is setting a target far below current performance. If your actual CPA is $80 and you set a $25 target, the system simply stops bidding on most auctions and volume collapses. The safer path is to start at or slightly above your recent average CPA, then step the target down 10-15% at a time, waiting for the learning period to settle between moves. Also watch for a target that is too generous: tCPA will happily spend the full budget hitting an easy number when a tighter one would have been achievable.
Opus Growth exposes bidding strategy management as a real write action, so you can ask your AI assistant to review a campaign's actual CPA against its target and change it in the same conversation across Google Ads and Microsoft Advertising. The proposed change is returned as a dry run showing exactly what will be modified, and nothing is applied to the live account until you approve it.
Frequently asked questions
As a working rule, aim for at least 30 conversions in the last 30 days on the campaign. Below that the model has too little signal, and Maximize Conversions without a target — or manual bidding — will usually be more stable until volume builds.
No. It is an average the system optimizes toward, not a cap. Individual conversions can cost well above or below the target, and daily CPA will fluctuate; judge performance over weeks, not days.
An aggressive cut makes most auctions unprofitable at the new bid ceiling, so the system stops entering them. Revert closer to your historical CPA and reduce in 10-15% increments, allowing the learning period to complete between each change.
