Google Ads Bidding Strategies: Target ROAS vs Target CPA by Data Volume

Which Google Ads bidding strategy should I use?

Choose based on how many conversions the campaign recorded in the last 30 days and how much your order values vary. Your industry, product category or what a competitor uses matters far less. Smart Bidding is only as accurate as the data it learns from, and a tight target on thin data forces the system to guess, which usually ends with impressions drying up.

For e-commerce, four strategies do most of the work:

• Maximize conversions: spends your budget to get as many conversions as possible and ignores what each order is worth.
• Maximize conversion value: spends your budget to get the highest total conversion value, in other words revenue. Without a ROAS target it aims to spend your full average daily budget.
• Target CPA: gets as many conversions as possible while keeping the average cost per acquisition close to the number you set.
• Target ROAS: aims for the average conversion value you want back for every dollar you spend.

We won't re-explain how ROAS is calculated here; if you need the basics, start with our guide to ROAS. This post is about when to move from one strategy to the next and how to manage the target once you do.

How many conversions do you need for each bidding strategy?

The rule of thumb: don't set a target while data is thin, then tighten the target as data builds up. The minimums in Google's own help pages tell you where each step up makes sense.

We turned those thresholds into a four-stage model. The stages are our recommendation; the thresholds come from Google's documentation.

Two caveats. First, the 15-conversion minimum is counted at the conversion tracking level, so a brand-new campaign can lean on the account's wider history. Second, Google says Target CPA can start with no conversion history at all, but it recommends measuring against at least 30 conversions over 30 days before judging whether the target is being hit. Other campaign types have their own bars: Demand Gen, for example, needs at least 50 conversions in 35 days for Target ROAS.

Target ROAS vs Target CPA: what's the difference?

Target ROAS bids according to what an order is worth; Target CPA treats every conversion as equal. For a store selling $15 accessories and $900 products in the same campaign, that difference is huge.

A practical decision rule: look at the last 90 days of orders. If your largest baskets are several times the size of your smallest, lean toward Target ROAS. If most orders cluster around the same value, Target CPA gets you a similar result with less volatility. Either way, clean data matters more than the strategy label; in Shopping, value bidding only works as well as your product data, which is why feed optimization comes first.

What should my target ROAS be?

Start at or slightly below the ROAS you actually achieved in the last 30 days, and let your break-even point set the floor. When you create a strategy, Google suggests a target based on recent performance. For Target CPA, the suggested value is your average CPA over the last 30 days, adjusted for conversion delay. Treat that suggestion as a starting point, then check it against your own profitability math.

1. Measure actuals Pull the last 30 days of spend and conversion value. Example: $6,000 spend and $30,000 conversion value, which is a 500% ROAS.
2. Find the floor With a 40% gross margin, break-even ROAS is 1 ÷ 0.40 = 250%. Any target below that loses money on every sale.
3. Set the start Put the first target at 450–500%, just under your actuals, so the system keeps current traffic while it learns.
4. Wait and measure Give it 1–2 full conversion cycles before judging, which is what Google recommends. If most orders arrive within 5 days of the click, that means roughly 5–10 days at minimum. Leave the last few days out of your read, because delayed conversions may not have arrived yet.
5. Tighten gradually If volume holds and your profit goal is higher, raise the target in small steps.

With Target ROAS, Google also asks you to be comfortable with daily spend reaching up to twice your average daily budget. Monthly spend won't exceed your monthly limit, but day-to-day swings are normal.

When should you change your bid strategy or target?

Don't touch the target until learning has finished and at least one conversion cycle has passed; when you do change it, move in small steps. According to Google, the "Learning" status appears after a new strategy, a setting change, or a composition change (campaigns, ad groups or keywords added to or removed from the strategy). Google says calibration typically takes a few conversion cycles (1–2 is typical), and can be faster when there is plenty of conversion data. The algorithm also keeps learning after the "Learning" label disappears.

Google does not publish an official percentage for how much to change a target at once. Here is the rule we use:

• Don't move the target more than roughly 10–15% at a time. Example: go from 500% to 550%, measure, then to 600%.
• Wait at least one full conversion cycle between changes. If most orders arrive three days after the click, don't decide on three days of data.
• Don't change target, budget and campaign structure in the same week, or you won't know which change caused the result.
• Turn big changes into tests. In the Target CPA or Target ROAS settings, "Save as experiment" runs the new target side by side with the old one.
• If "Learning" drags on for more than two weeks, audit conversion tracking first. The problem is usually missing or double-counted conversions, not the bid.

Switching strategy entirely, say from Maximize conversions to Target ROAS, only makes sense once the next stage's threshold has been cleared consistently over 30 days, not after one strong week. For a wider account health check, use the review order in our Google Ads optimization guide.

How does the August 17, 2026 bidding change affect your targets?

Budget-limited campaigns on target-based bidding now bid closer to the target you entered, not the performance they had been delivering. Google rolled this out from August 17, 2026 across Search, Shopping, Performance Max, Demand Gen, Display, Hotel and Travel campaigns. App campaigns, video reach and video view campaigns are excluded.

Google's own example: a budget-limited campaign with a $10 Target CPA that was actually converting at $5 will now trend toward $10 CPA unless the target is updated. The same logic applies to Target ROAS. A campaign with a 400% target that has been running at 550% may start bidding more aggressively toward 400%.

Old targets left alone for years because "it's beating the target anyway" are exactly the ones this change exposes. As of September 2026, the tool's labels may differ slightly by account; start with campaigns flagged as limited by budget.

When does a portfolio bid strategy make sense?

Use a portfolio strategy when several Search or Shopping campaigns share the same profit target but none of them generates enough data on its own. A portfolio bid strategy groups campaigns, ad groups and keywords under one target and pools their data, so three campaigns with 10 conversions a month each look like one 30-conversion pool to the algorithm.

• Where: portfolio strategies are stored and managed in the Shared library.
• Upside: maximum and minimum CPC bid limits are only available on Search and Shopping portfolio strategies, and they apply in Search Network auctions only. Google doesn't recommend them for Target ROAS, but they are a safety net if CPCs spike.
• Limit: portfolio strategies aren't available for Performance Max, which runs on its own campaign-level Target ROAS.
• Trap: adding or removing a campaign is a composition change and restarts learning, so keep the portfolio stable.

Don't put categories with very different margins, say 60% private label and 15% electronics, in the same portfolio. A single target will always misprice one of them.

Should you change targets for sales and promotions?

For a short, unusually strong event, leave the target alone and use a seasonality adjustment instead. Smart Bidding already accounts for recurring seasons such as the holidays. Seasonality adjustments are for unusual periods the system can't learn from history. If you expect a 3-day flash sale to lift conversion rate by 50%, you schedule an adjustment that raises expected conversion rate by that amount for those 3 days.

To create one, click the Tools icon, open Budgets and bidding, choose Adjustments, then the Seasonal tab, and pick "Conversion rate" as the adjustment type. Adjustments are supported on Search, Shopping and Display campaigns using Target ROAS or Target CPA, and on Performance Max with any bid strategy. You don't need to reverse anything afterward; bidding returns to normal when the event ends.

Next steps: what to do this week

Place every campaign in a stage, then make only one change per campaign. For most e-commerce accounts this fits into a single week:

• Export each campaign's conversions for the last 30 days and note which stage of the table above it falls into.
• Calculate break-even ROAS from your gross margin and fix any target that sits below it.
• Open the Bid Target Adjustment Tool for budget-limited campaigns and compare each target with actual performance.
• Keep a change log with the date and the previous value of every target change, so you can read learning time and impact later.
• Put the next two months of promotions on a calendar and prepare seasonality adjustments in advance where needed.

The conversion value Google reports rarely matches the revenue in your store dashboard exactly. To know which real revenue your target is anchored to, you need Google Ads, GA4 and store data side by side. Marpany's ad performance view puts that comparison in one place, and MrPany flags when a target looks out of line with actual results.