Target CPA vs Target ROAS: Which Bid Target to Set
In short: Both are target fields inside Google's Smart Bidding, but they optimize toward different math. Target CPA treats every conversion as interchangeable and holds an average cost per conversion. Target ROAS reads the value you send with each conversion and buys the valuable ones even when they cost more. If your conversions genuinely differ in worth, use tROAS; otherwise tCPA.
By the AdFlint research team · Fact-checked against current Google and Meta platform behavior · Last reviewed July 2026
Target CPA
Bids automatically toward a chosen average cost per conversion, letting individual conversions land above or below that number.
It now lives as a target field inside Maximize Conversions rather than a standalone strategy. Google bids up on auctions it expects to convert near your target and backs off elsewhere, so a target far below recent actual CPA simply throttles volume. Set it close to what the account already achieves, then move it in increments and let the learning period settle before judging the outcome.
Full definitionTarget ROAS
Bids automatically toward a chosen ratio of conversion value to ad spend, entered as a percentage in Google Ads.
It is the target field inside Maximize Conversion Value, and it only functions when your conversion values are accurate and varied. Google predicts value per auction and bids up where it expects payback. Raising the target reduces volume, and that trade is the mechanism rather than a defect. The common error is picking an aspirational number the account has never reached, which starves delivery outright.
Full definitionSide by side.
The differences that actually change what happens in your account.
| Target CPA | Target ROAS | |
|---|---|---|
| What you enter | A currency amount - the average you want to pay per conversion. | A percentage - conversion value divided by spend. |
| Conversion values required | No. Every conversion is weighted the same. | Yes. Values must be real and varied or it degrades to counting. |
| Lives inside | Maximize Conversions, as its optional target field. | Maximize Conversion Value, as its optional target field. |
| What tightening it does | Declines auctions predicted to cost above the target. | Declines auctions predicted to return below the ratio. |
| Typical fit | Lead gen, calls, bookings where each conversion is worth about the same. | Ecommerce with varied basket sizes, or leads scored to real values. |
| Failure mode | Target set below achievable CPA, which starves delivery. | Hardcoded conversion value, making the reported ROAS confident and meaningless. |
What actually separates them.
tCPA constrains cost per conversion, while tROAS constrains the ratio of value returned to spend and will happily pay a higher CPA for a bigger order.
tROAS only functions when conversion values vary; with one flat value per action it behaves like tCPA wearing a percentage.
tCPA sits inside Maximize Conversions and tROAS inside Maximize Conversion Value, so you pick the strategy first and the target second.
Raising a tROAS target and lowering a tCPA target both tighten efficiency and cut volume, but they move in opposite numeric directions.
A tROAS campaign can look expensive on cost per conversion while being the more profitable of the two, so the reporting yardstick has to change with the target.
Which one should you use?
Use Target CPA when
- Every conversion is worth roughly the same - a booked call, a demo request, a trial signup.
- You have no reliable revenue figure to pass back with the conversion.
- You are managing to a cost ceiling agreed with finance rather than a margin ratio.
- Lead quality is only scored offline weeks later, so no usable value exists at conversion time.
Use Target ROAS when
- Order values vary widely and you send the actual revenue with the purchase event.
- Margins differ enough by product that treating every conversion as one unit is misleading.
- You can compute a break-even return and want the bidder to respect a floor above it.
- Subscription or lifetime values are being fed back through offline conversion imports.
ROAS Calculator
Enter ad spend, revenue, and profit margin to get ROAS, ACOS, break-even ROAS, net profit, and ROI in one place.
Open the free calculatorCommon questions.
Can I run Target CPA and Target ROAS in the same campaign?
No. A campaign uses one bid strategy, and the two targets belong to different ones - tCPA to Maximize Conversions, tROAS to Maximize Conversion Value. You can split traffic across campaigns and run one of each, but inside a single campaign you choose which constraint the bidder honors.
My Target ROAS campaign's CPA went up. Is something broken?
Usually not. Value bidding is allowed to pay more per conversion when it predicts a larger order, so a rising cost per conversion alongside rising revenue is the strategy working as designed. Judge it on conversion value and return over a full conversion window, or you will optimize away your best buyers.
How far can I move a target at once?
Move in increments and let each change settle through the learning period before judging it. A large jump asks the model to re-price every auction against a target it has no data near, which usually shows up as a delivery drop rather than a clean efficiency gain. Small, spaced changes hold volume much better.
Or stop choosing between them.
AdFlint picks the setting, writes the ads, and keeps optimizing inside the Google and Meta accounts you already own.
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