Both strategies automate your bids, but they chase different goals. The target CPA vs target ROAS decision comes down to one question: do your conversions all have about the same value, or do they vary a lot? This guide explains what each strategy does, what it needs and how to choose between them.
In this guide: What Target CPA Does | What Target ROAS Does | Target CPA vs Target ROAS: The Core Difference | How to Choose | Setting the Target | Common Mistakes | Frequently Asked Questions | Final Thoughts
What Target CPA Does
Target CPA sets bids to win as many conversions as possible at an average cost per conversion that you choose. Google’s help page on Target CPA explains that some conversions will cost more than your target and some less, and the aim is to land on the target on average.
At each auction, the system estimates a bid from past campaign data and live signals such as device, location, time of day and remarketing lists. It treats every counted conversion as equal.
What Target ROAS Does
Target ROAS is the value-based counterpart. Instead of counting conversions, it aims for a return on ad spend: a set amount of conversion value for each unit of cost. Google’s page notes that the strategy was previously labelled “Maximize conversion value with a target ROAS” and is now simply called Target ROAS.
It needs conversion values to be reported with each conversion. If a conversion has no value attached, the strategy has nothing to work with. Our guide to what counts as a good ROAS helps you set a realistic number.
Target CPA vs Target ROAS: The Core Difference
Target CPA asks “how many conversions can I get at this cost?” Target ROAS asks “how much value can I get for this spend?” The first treats a small order and a large order the same. The second pushes spend toward the searches that tend to bring larger values.
A hypothetical example
Imagine two advertisers who each pay about 50 per conversion. The first sells one service at a fixed price, so every lead is worth roughly the same. Target CPA fits well. The second sells products from 20 to 500, so a conversion could be worth very little or a great deal. Target ROAS fits better because it can tell those conversions apart. These numbers are hypothetical and only illustrate the logic.
How to Choose
Use these questions as a quick filter.
- Do conversions vary in value? If yes, and you track the values, lean towards target ROAS. If they are similar, target CPA is simpler.
- Is your value data reliable? Wrong values lead to wrong bids. If values are guesses, start with target CPA.
- What does your business measure? Lead generation teams often think in cost per lead. Online shops often think in revenue per unit of spend.
- How much data do you have? Both strategies learn from conversion history, and more history usually gives steadier results.
Our overview of Google Ads bidding strategies shows where these two sit among the other options.
Setting the Target
With history, Google suggests a starting target based on your average CPA over the last 30 days, adjusted for conversion delays. Without history, the target comes from your business goals. You can begin without any conversion history, but tracking must be in place first.
Avoid setting the target too tight. Google warns that a target set too low can make you miss clicks that would have converted, which reduces total conversions. Move the target in small steps rather than large jumps.
When you review results, compare the actual CPA with the average target CPA shown in the report, rather than the number you typed in. The average reflects traffic mix, device adjustments and any changes you made over time.
Common Mistakes
- Changing the target every few days, which keeps the system from settling.
- Judging results on a handful of conversions. Google suggests evaluating over the last 30 days with at least 30 conversions.
- Setting ad group targets. Google says these are possible but not recommended, because they can restrict Smart Bidding.
- Adding bid limits to a portfolio strategy without a reason. Google does not recommend them.
- Forgetting that the “Include in conversions” setting decides which actions the strategy optimizes for.
Both strategies sit within Smart Bidding, so the same habits apply: clean tracking, patience and one change at a time. If you want to test a switch, Google offers a “Save as experiment” option that compares new settings with the original campaign.
Frequently Asked Questions
Can I switch from target CPA to target ROAS?
Yes, but treat it as a test. Make sure conversion values are reported accurately first, and compare results over a full evaluation window before you commit.
Do I need conversion history to use target CPA?
No. Google says you can start without history, though the system has less to learn from, so expect results to settle as data builds.
Which strategy is better for lead generation?
Target CPA is often the simpler choice when all leads have a similar value. If you can pass back the real value of each lead, target ROAS becomes worth testing.
Final Thoughts
The target CPA vs target ROAS choice is really a question about your data. If conversions are worth about the same, use target CPA. If values differ and you can measure them well, target ROAS lets the system favour the valuable ones. Pick one, set a realistic target and give it time.
Want expert help with your account? See our Google Ads management service.