Most advertisers running Performance Max in 2026 are working from incomplete information. Not because PMax is broken — it isn’t. But because the numbers Google shows you and the numbers that actually matter are two different things.
PMax now accounts for 19.9% of total Google Ads spend, up from 16.7% in 2024. That’s a 19% increase in a single year, according to Fluency’s 2026 benchmark report. In 2025, PMax delivered 51.1 billion impressions for Fluency clients, compared to 7.8 billion from Google Search. 71% of advertisers now use it, up from 60% in 2024.
The experiment is over. PMax isn’t a test campaign type anymore. The question is what you’re actually getting for that budget.
What the ROI Data Looks Like Outside of Google’s Dashboard
Cassandra analyzed 253 Marketing Mix Models across 59 advertisers, covering $383 million in total media spend. The goal: measure actual incremental ROI — what your spend caused, isolated from attribution overlap, seasonality, and cross-channel halo effects.
| Campaign Type | Median Incremental ROI | 95% CI |
|---|---|---|
| Search Non-Brand | 5.21x | Narrowest range |
| Performance Max | 4.64x | 3.11x – 6.41x |
| Search Brand | 4.14x | — |
Those numbers are consistently lower than platform-reported ROAS — by a factor of two to five times — because they measure incremental impact rather than last-click attribution. Platform ROAS tells you what Google attributed to a campaign. Incremental ROI tells you what would not have happened without it. Those are different questions with very different answers.
The honest read: PMax is consistent. The 95% confidence interval runs from 3.11x to 6.41x. You’re unlikely to hit the extremes. For advertisers who want predictable performance across Google’s full inventory without managing separate Search, Shopping, Display, and YouTube campaigns, that consistency has genuine value.
What PMax doesn’t offer is transparency into where that budget went. In Cassandra’s analysis covering $66 million in PMax spend, most advertisers could not break down what portion went to Search, Shopping, Display, or YouTube. You’re buying a bundle and trusting Google’s algorithm to distribute it.
The Transparency Problem Is Getting Fixed, Slowly
PMax launched with a structural criticism baked in from day one: you hand over creative assets, audience signals, and budget, and Google decides everything else. That was a reasonable trade when PMax was generating strong platform-reported ROAS. It became harder to defend when advertisers started asking how much of that ROAS was just capturing branded traffic they would have gotten anyway.
Google has been addressing this incrementally:
- January 2026: Channel performance reporting and Search Partner Network segmentation rolled out to all accounts.
- April 2026: Demographic breakdowns by age and gender added — something Search and Display have had for years.
- Now: Account-level placement exclusions apply simultaneously across PMax, Demand Gen, YouTube, and Display — no more replicating exclusion lists per campaign.
None of this changes how PMax works at its core. But it gives you enough data to manage the campaign rather than just monitor it. That’s a meaningful difference.
The cannibalization problem: A PMax campaign running without brand exclusions will frequently serve ads to users already searching your business name — inflating ROAS considerably. The fix is straightforward: apply brand exclusions. Many accounts still don’t have them in place.
What the Data Says About When to Use PMax vs Search
The Cassandra benchmarks are clear on one thing: Search Non-Brand outperforms PMax on incremental ROI at the median. That’s not a knock on PMax (4.64x is a solid return), but advertisers who treat PMax as a replacement for well-structured Search campaigns are likely leaving returns on the table.
The more useful framing is that PMax and Search serve different functions:
- Search captures high-intent queries from users actively looking for what you offer.
- PMax runs discovery-based targeting across Google’s full inventory, finding audiences who might convert rather than those already signalling intent.
Optmyzr’s research found that PMax campaigns allocating 50% or more of account budget achieve 625% ROAS at maturity versus significantly lower performance for lower-allocation campaigns. The implication: PMax needs volume. If you’re running it on a tight budget below 30 conversions per month, standard Shopping or Search campaigns typically outperform it because they don’t require the learning-phase data PMax depends on.
What to Actually Do With This
- Run brand exclusions if you haven’t already — this is the single highest-leverage fix for most accounts.
- Check your channel performance report (available now in all accounts) and look at where your PMax budget is actually going.
- Pull demographic data and see if the age and gender distribution matches your actual customer profile.
- Run Search Non-Brand alongside PMax — not instead of it. The data from Cassandra’s analysis suggests most advertisers see higher incremental returns from a split approach.
- If you’re below 30 conversions/month, standard Shopping or Search will likely outperform PMax until your account has the data volume it needs.
PMax works. It delivers consistent returns, it scales across Google’s full inventory, and the transparency improvements in 2026 make it genuinely more manageable than it was a year ago. But consistent doesn’t mean optimal. The benchmarks exist now — use them to set expectations that don’t depend on Google’s attribution logic.