It is precise but generous. Google Ads usually captures the purchases that followed a Google ad click quite reliably, since search clicks are close to the sale and easy to track. Where it overstates is in what those clicks deserve credit for. Branded search, Shopping for your own products, and the remarketing parts of Performance Max all collect demand that other channels created. So Google’s reported ROAS is often the most believable-looking number in your stack and one of the most inflated.
Why does Google’s ROAS look so good?
Search sits at the bottom of the funnel. Someone sees your Meta ad, hears a podcast mention, or gets a friend’s recommendation, then searches your brand name and clicks a Google ad. Google records a high-ROAS conversion. It was a real click and a real sale, but the click did very little of the persuading. I explained why this makes Google look stronger than Meta in why is Google Ads ROAS higher than Meta ROAS.
What about Performance Max?
Performance Max mixes inventory across Search, Shopping, YouTube, Display, and more in one campaign, and it is very good at finding people already close to buying, including existing customers and brand searchers. That pushes reported ROAS up without telling you how much of it is new demand. If PMax is a large share of your spend, look at how much of its revenue comes from returning customers and branded queries before you scale it. More in do attribution tools work with Google Performance Max.
Are there reporting quirks to know?
A few. Google Ads uses data-driven attribution by default, which spreads credit only across Google touchpoints, so other channels never get a share. Conversions are reported against the date of the ad interaction rather than the order date, so recent days keep filling in for a while and will not match Shopify’s daily revenue. Some conversions are modeled when consent or browser limits block direct tracking. And conversion value is whatever you send Google, so if refunds, tax, or shipping are handled differently than in your store reports, the ROAS will not reconcile.
How can I check it?
Split your Google spend into branded search, non-branded search, Shopping, and PMax. Branded search ROAS will almost always be the highest and the least meaningful. Then compare Google’s reported revenue to the orders your store can tie to Google by last click with UTMs, and to the share of new customers among those orders. If most of Google’s revenue is branded and returning, its true incremental ROAS is much lower than the dashboard shows.
The most useful single test is a branded search holdout. Pause or sharply cut branded search in a few regions for two to four weeks and watch total revenue there. If it barely moves, organic results were catching those buyers anyway. I wrote about doing this honestly in brand search is the easiest thing to test.
What should I use for budget decisions?
Use Google’s reporting to manage inside Google, comparing campaigns, keywords, and products. For deciding Google’s share of total budget, use MER plus a deduplicated attribution source that credits each order once across all channels and splits new and returning customers. ThoughtMetric does that across Google, Meta, TikTok, Microsoft, and other channels, with product-level attribution that helps judge Shopping and PMax. (Disclosure: ThoughtMetric sponsors this site.) It starts at $99 a month for 50,000 pageviews.
Quick answers
- Does Google track its own clicks accurately? Mostly, yes.
- Does its ROAS reflect what Google caused? Not on branded search and much of PMax.
- Why won’t it match Shopify by day? Google reports on click date and may model some conversions.
- Best single check? A branded search holdout, read against total revenue.
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