How to measure Performance Max, step by step

To measure Performance Max, check what it counts, then where it served, then what it added. Read the purchase action's windows, the channel performance report and the search terms report in Google Ads. Find its visits under Cross-network in GA4. If you can, finish with an uplift experiment, which usually settles more than any report.

Open Google Ads and GA4 side by side and give it an hour. Steps 1 to 7 read what Google claims. Steps 8 and 9 hold it against GA4. The last step is the only one that tests anything.

Write each number down with its date range and settings. Google's reports move when the settings do, and a number without its settings starts arguments.

Step by step

1. Read the purchase action's windows. Performance Max bids toward the conversion actions you choose, so start with what they count. Google's defaults are 30 days after a click, 3 days after an engaged view and 1 day after a view. Menu path: Goals > Conversions > Summary > your purchase action > Edit settings.
2. Open the channel performance report. It splits the campaign across Search, Maps, YouTube, Discover, Gmail and the Display Network, in a summary, a chart and a table. Dates before June 6, 2025 are not in it. Menu path: Campaigns menu > Campaigns > Insights and reports > Channel performance.
3. Segment by Ad event type. This shows whether each conversion followed an engaged view, a click, an interaction or an impression. Clicks are the part with a visit GA4 can see. Menu path: Channel performance > Segment on the table toolbar > Ad event type.
4. Read the search terms. The report lists the searches behind Performance Max ads, with Shopping and text ads told apart, from March 2023 onward. Count the conversions on searches that contain your brand name. Menu path: Campaigns menu > Search terms > Search terms and landing pages for Performance Max.
5. Check where the searches came from. Search terms insights groups searches into categories, and its source column shows keywordless targeting or your own search themes. Menu path: Campaigns menu > Insights > search terms insights card.
6. Split new and returning buyers. With a customer acquisition goal and purchase optimization, a segment splits conversions into new and returning customers. Under Google's auto-detection, a purchase in the last 540 days makes a buyer returning. Menu path: Campaigns table > Segment > New vs. returning customers.
7. Keep brand searches out if a brand campaign covers them. Brand exclusions keep Performance Max off searches for your brand on Search, Shopping and YouTube search inventory. A checkbox can still allow Shopping ads there. Menu path: Campaigns > Settings tab > your campaign > Additional settings > Brand exclusions.
8. Find the campaign in GA4. GA4 files Performance Max visits under Cross-network, next to Demand Gen and Smart Shopping. The Google Ads campaigns report then lists the campaign with clicks, cost and key events. Menu path: GA4 > Advertising > Key event performance > Google Ads. For the channel view, use Reports > Acquisition > Traffic acquisition.
9. Download the paths and check position. The paths report shows which channels open, assist and close key events, in early, mid and late touchpoints. Early means the first 25% of a path. Menu path: GA4 > Advertising > Key events > Key event attribution paths > Share this report.
10. Test what it adds. An uplift experiment runs Performance Max next to comparable campaigns, with a traffic split of 50% by default. If your account has access, Conversion Lift based on geography compares regions with and without ads. Menu path: Campaigns menu > Experiments > plus button > Campaign types > Performance Max Uplift > Continue. For geo lift: Goals > Lift measurement > plus button > Conversion Lift under Based on Geo.

A worked example

Here is one month of Performance Max, with round numbers made up for illustration.

For illustration, the 50 view-led conversions have no matching visit in GA4, so GA4 cannot back them. In this worked example, the 60 brand-search conversions came from people who typed your name into Google. In the worked example, only the last 90 are a real question, and the last step is how you ask it.

For illustration, suppose the uplift test then finds the arm with Performance Max ahead by 40 conversions. In the worked example, that 40 is the figure to weigh against the campaign's cost, not the 200. It is still counted in Google Ads conversions, so check total Shopify orders for the same weeks as well.

Now the GA4 side, from one store's real export. Store A is one store's anonymised GA4 export, 1 January 2024 to 21 August 2026, holding shares of revenue only. On its Channels sheet, the touched view adds up to 110.4%, because a journey that touched two channels counts in both. Ad platforms add up the same way: Google Ads and Meta can each claim one shared sale in full.

On its Journeys sheet, one-touch journeys carry 79.5% of revenue and close in 0.5 days. If your brand-search buyers look like that, they arrived ready to pay. The uplift test in the final step tells you whether they would have paid without the ad.

What to check when the report looks wrong

• Google Ads shows far more conversions than GA4's Cross-network row. Check step 3 first: engaged-view conversions count in Google Ads and not, by default, in GA4. For the rest of the gap, read why Google Ads shows more conversions than GA4.
• Brand Search conversions fell when Performance Max launched. Check step 4 for your brand name, then check whether the brand campaign hit its budget. Google says Performance Max may serve on exact match terms when a Search campaign is limited by budget.
• The channel report will not go back past June 2025. That is where its data starts. For older months, compare campaign totals only.
• A channel shows no spend. Read the Status column first. If it shows no issue, Google says Performance Max may simply be bidding on channels it expects to return more at that moment.
• Store visits vanish from the search terms view. Store visits and store sales are not available in that report, so its totals run lower than the campaign's.
• New customer counts shifted from October 2025. Google began estimating whether Unknown buyers were new or existing, based on past campaign performance. Compare periods on one side of that change.

What to do this week

1. List the windows of every purchase action. In Goals, open Conversions, then Summary, and open each purchase action. Pass: one primary purchase action, with click, engaged-view and view windows you can name. Fail: several purchase actions with different windows, so the campaign chases and reports a mix.
2. Find last month's Cross-network row in GA4. In Reports, open Acquisition, then Traffic acquisition. Pass: Cross-network shows sessions and purchases, so GA4 sees the campaign's clicks. Fail: it is empty, so check auto-tagging and the Google Ads link before you read anything else.
3. Read where Cross-network sits in the paths report. In GA4, open Advertising, then Key event attribution paths under Key events. Pass: it earns credit in early or mid touchpoints. Fail: it only shows up late, so it mostly closes journeys that other channels opened.

Check the homework. Your GA4 Attribution paths export already holds the evidence. Causality Engine reads that one file and shows what each channel caused next to what last-click gave it, in 1 to 2 minutes, for €99 once (excluding VAT), refundable within 30 days. Check the homework

Sources, 1 October 2026: About conversion windows (Google Ads Help); About Performance Max campaigns (Google Ads Help); About the channel performance report for Performance Max (Google Ads Help); About the search terms report in Performance Max (Google Ads Help); About search terms insights (Google Ads Help); Evaluate Performance Max Results (Google Ads Help); Measure your lifecycle goals campaigns (Google Ads Help); Apply brand exclusions to Performance Max or Search campaigns (Google Ads Help); Default channel group (Google Analytics Help); Google Ads campaigns performance report (Google Analytics Help); Key events attribution paths report (Google Analytics Help); Set up Uplift experiments for Performance Max (Google Ads Help); Set up Conversion Lift based on geography (Google Ads Help); Performance Max reporting in Google Analytics (Google Ads Help); Traffic acquisition report (Google Analytics Help).

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