A Performance Max campaign for ecommerce works when the target ROAS comes from the margin of each product, the feed is split by profit tier, and searches for your own brand are left out. Without those three adjustments, PMax tends to show a nice-looking ROAS driven by people who were going to buy anyway, while spending more on the products that earn the least profit. This guide shows the setup we use for online stores, with the margin math and the step-by-step.
This article is for people who have already decided to use PMax. If you’re still deciding whether to use it, start with Performance Max: when to use it and when to avoid it.
What a Performance Max campaign does in a store
PMax shows your products across all Google channels from a single budget and decides on its own where to spend, based on the goal you give it. On the official Performance Max page, Google lists YouTube, Display, Search, Discover, Gmail and Maps.
For ecommerce, Shopping carries the most weight. The showcase with photo and price that appears in search comes from the Merchant Center feed, the same one used for Google Shopping. PMax uses that feed and adds the other channels on top.
That’s where the risk is. It optimizes for the goal it receives, and if the goal is revenue, it chases revenue. Profit doesn’t enter its calculation unless you put it in.
Cheap clicks, tight margins
In retail, clicks tend to be cheap, and margin decides whether the campaign is profitable. Our CPC by industry study shows this clearly. The retail industries all came in below the median of R$4.96 across the 103 industries, based on the top-of-page bid estimated by Google in October 2026, not what each company actually pays.
| Retail industry | Estimated top-of-page bid (Oct 2026) | Combined monthly searches |
|---|---|---|
| Pet shop | R$2.82 | 440.500 |
| Optical stores | R$2.65 | 464.500 |
| Florists | R$1.84 | 809.600 |
| Fashion | R$1.72 | 421.300 |
| Furniture | R$1.42 | 825.000 |
| Electronics | R$1.17 | 2.371.000 |
| Shoes | R$0.84 | 844.000 |
A R$0.84 click in footwear looks like a gift. But if the margin on a sneaker is 15%, every R$100 in sales leaves R$15 to pay for ads, free shipping, returns and everything else. The campaign can sell a lot and still lose money.
Search demand for the topic in Keyword Planner, in October 2026, is small and expensive. “Campanhas performance max” gets 50 searches a month, “performance max ecommerce” gets 10, and the top-of-page bid reaches R$46.52. Whoever searches for this already advertises and has a problem.
How to calculate target ROAS from margin
Break-even ROAS is 1 divided by the contribution margin. Below it, every sale that came from an ad costs more than it earns.
Contribution margin is what’s left of the price after product cost, taxes, payment processing fees, subsidized shipping and marketplace commission, if any. It’s not the gross margin from the supplier’s spreadsheet.
| Contribution margin | Break-even ROAS | Target ROAS to start with |
|---|---|---|
| 50% | 2,0 (200%) | 250% |
| 35% | 2,86 (286%) | 340% |
| 25% | 4,0 (400%) | 470% |
| 15% | 6,67 (667%) | PMax alone isn’t worth it |
The right-hand column adds a cushion of about 20% over break-even to cover returns and cancellations. A product with a 15% margin almost never holds up with paid ads, unless repeat purchases are high. That’s a figure only you have.
Before turning on target ROAS, Google requires history. On the target ROAS bidding page, the requirement for Search and Shopping is at least 15 conversions in the last 30 days, and the conversion value must be getting sent. The same page notes that, since June 2026, the strategy appears only as “Target ROAS”, without “Maximize conversion value” in front. The behavior is the same.
The feed split by margin
Splitting the feed by margin is the adjustment that changes the result of a store’s PMax the most. The idea is that each product group gets its own goal, instead of an average goal that favors the wrong products.
Merchant Center has five custom labels, from custom_label_0 to custom_label_4, which you fill in as you like. Here’s how we use them.
- In custom_label_0, tag each product’s margin tier. For example, high, medium and low.
- In custom_label_1, tag the product’s role. Bestseller, new release, end-of-stock item.
- Create one Performance Max campaign for each margin tier, each with its own target ROAS taken from the table above.
- Inside each campaign, split the asset groups by category, with images and text for that category.
- Keep low-margin products in a campaign with a high target or out of paid ads.
The product title is part of the feed too. Start with what people type, with product type, brand, model and the attribute that sets it apart, like size or color. A creative title doesn’t show up in any search.
If your store still isn’t sending the sale value correctly, the problem comes before PMax. Purchase tracking with value, reinforced with enhanced conversions, is what gives target ROAS something to rely on.
Brand exclusion and negative keywords
Exclude searches for your own brand from PMax and let a separate search campaign handle them. Without that, PMax picks up people who were already going to buy, counts the sale as its own, and the ROAS looks much better than it is.
Google documents three controls for this on the official PMax page. Brand exclusions, campaign-level negative keywords, and search themes to guide intent. The same page explains the order of priority. A search campaign with the exact keyword wins over PMax when the search matches that exact keyword, but if the search campaign is limited by budget, PMax may show up instead.
That’s why the brand campaign needs a budget that doesn’t run out midday.
In a store, these are usually the first negatives.
- Searches for jobs, openings, suppliers and wholesale, when you only sell at retail.
- Names of competing brands you don’t resell.
- “Free”, “used” and “repair”, depending on the product.
What to check in the report after 30 days
The average ROAS of a Performance Max campaign is misleading, because it mixes brand, remarketing and new customers. Before judging, open these reports.
- Product performance, to find the item that spends and doesn’t sell.
- Search insights, to see which search themes are bringing sales.
- Channels, to know how much went to Shopping, YouTube and Display.
- Sales from new and returning customers, when the acquisition goal is turned on.
If more than half of your sales come from existing customers, the campaign is harvesting, not planting. That’s not bad in itself, but it changes how you read the results and how much a bigger budget is worth.
One warning. Raising the budget or changing the goal several times in the same week tends to make a campaign unstable. We change one thing at a time and wait at least one full week of data.
Who should set this up and manage it
Setting up a store PMax campaign requires access to Merchant Center, Google Ads and your company’s margin numbers. If the person managing the account doesn’t ask about your margin, they will optimize for revenue.
When you hire, ask how they define the target ROAS, whether they split the feed by margin, how they handle brand search, and whether the report shows profit or just ROAS. The general guide to channels for online stores is in e-commerce marketing.
Frequently asked questions
Is a Performance Max campaign worth it for e-commerce? It is when the feed is in good shape, purchases are tracked with value, and the goal comes from your margin. For a new store with no conversion history, a Shopping or search campaign usually learns faster and shows you more of what’s happening.
How do you create a Performance Max campaign in Google Ads? Link Merchant Center to Google Ads, choose the sales goal, set the budget and bidding strategy, build asset groups by category, and add brand exclusions and negative keywords before publishing.
How does a Performance Max campaign work? It combines your feed, images, text and bidding goal, and uses Google’s AI to decide which channel and which audience sees each ad. You control the goal, budget, assets and exclusions, not the channel of each click.
What’s the difference between Performance Max and a Shopping campaign? Shopping only shows the product showcase in search and gives you more control over products and bids. PMax uses the same feed and adds YouTube, Display, Gmail, Discover and Maps, with less visibility into where each dollar was spent.
Performance Max or a search campaign? One doesn’t replace the other. Exact match search has priority and works for your brand and the terms you want to control. PMax takes care of the catalog and the other channels.
Where to start
If your store already runs PMax, the free Google Ads audit shows how much of your sales comes from your brand, which products spend without selling, and whether the purchase value is being passed correctly. To hand setup and tuning to people who do this every day, see Ciclicko’s Google Ads management.