How do I split budget between Google and Meta?
Usually by job, not by reported ROAS. Google search and Shopping mostly catch people already looking for what you sell, while Meta mostly finds people who are not looking yet. Fund each until a test shows its extra sales no longer clear your break-even, then move money in small steps.
By Joris van Huët, Founder & CEOUpdated 7 min read
Run the numbers for your store: the free ad platform over-reporting checker.
Usually, split by job, not by reported ROAS. Google search and Shopping mostly catch people already looking for what you sell. Meta mostly finds people who are not looking yet. Fund each job until a test shows its extra sales no longer clear your break-even, and move money in small steps.
The usual answer is a fixed ratio, or a shift toward whichever dashboard shows the higher ROAS. Both assume the two dashboards measure with one ruler. They don't, and the gap between the rulers can decide a split before performance gets a say.
What one store's data shows
The split question turns out to be a timing question. One store's export shows why.
One store's anonymised GA4 export, 1 January 2024 to 21 August 2026. It holds shares of revenue only: no ad spend, no order counts.
| What the export shows | Share of revenue | Source cell |
|---|---|---|
| Journeys with 1 touch (0.5 days to buy) | 79.5% | Journeys sheet, 1 touch row |
| Journeys with 2 to 3 touches (12.5 days to buy) | 12.2% | Journeys sheet, 2-3 touches row |
| Journeys with 4 to 9 touches (16.9 days to buy) | 5.4% | Journeys sheet, 4-9 touches row |
| Journeys with 10+ touches (16.0 days to buy) | 3.0% | Journeys sheet, 10+ touches row |
| Direct, in last click, first click and touched views | 57.7% | Channels sheet, Direct row |
Start with the quick buyers. Journeys with 1 touch hold 79.5% of revenue on the Journeys sheet and take 0.5 days to buy. Every window on both platforms covers half a day. If such a buyer saw a Meta ad in the morning and clicked a Google ad at lunch, both platforms can claim the order. Add their reports together and one sale counts twice, which Do Google Ads and Meta double count sales? takes apart.
The slower journeys are where the two reports part ways. Journeys of 2 or more touches add up to 20.6% of revenue on the Journeys sheet (12.2% + 5.4% + 3.0%). On the Journeys sheet they take 12.5 to 16.9 days to buy. Google Ads keeps counting a click for 30 days by default, as its conversion window page explains. Meta's click window for website purchases is 1 or 7 days, per its attribution settings page.
So if days to buy count from the first click, a Google click that opened one of these journeys still counts in Google Ads. A Meta click that opened it has timed out, unless a later Meta click restarted the clock. Put the two ROAS figures side by side and slow buyers tilt the contest toward Google before anyone has caused anything.
Direct holds 57.7% of revenue on the Channels sheet in every view. In GA4, neither platform gets a cent of it. In their own reports, both can claim pieces: a Meta view, or a Google click days before the direct visit.
One more line: at a 40% margin, break-even ROAS is 2.5x on the Break-even sheet, because 1 divided by 0.40 is 2.5. It is arithmetic, not a ROAS the export reports. Each platform's extra sales have to clear that bar, whatever its dashboard says.
What the export cannot show: spend, orders, or either platform's own numbers. So it cannot say which platform earned more. It shows why their reports disagree before a single euro moves. One store, not a benchmark.
Why does comparing the two ROAS figures mislead?
Each platform grades itself with its own ruler. Google Ads uses data-driven attribution by default for most conversion actions, with that long click window. Meta's Results page lists 7-day click, 1-day view and 1-day engagement. One ruler is long and counts clicks. The other is short and counts views too.
They also hand work to each other. Someone sees a Meta ad, later searches your brand name and clicks your Google ad. Google Ads counts the click. Meta can count the view, if the purchase came within a day of it. Cut Meta, and part of Google's brand ROAS can fade with it. Is branded search worth paying for? covers that trap.
Both figures are also averages of money already spent. Your split decides where the next euro goes, and an average cannot price that euro.
Can GA4 settle it?
Partly. GA4 can put both platforms on one ruler. Tag your Meta ads with UTMs and import Meta's cost. GA4's All channels performance report then shows Ads cost and Return on ad spend for both, under one attribution model.
But GA4 sees clicks, not Meta views. Even its cross-channel budgeting models consider click-through conversions, YouTube engaged views and cost data. A Meta ad that someone only saw leaves nothing for them to count. The help page's own example moves $5,000 from Paid Social to Paid Search. Fair enough for an example. Just know which way the ruler leans.
The fair referee is a test. Google's own geo experiment guide describes a three-cell design for exactly this question. Google goes dark in one set of regions, the other platform in a second set, and both run as usual in the third. It asks for identical conversion windows on every platform, measured against "an independent, unattributed first party data source". For a Shopify store, that means sales by region. If switching a platform off feels too costly, raise one platform's spend in some regions instead. Google calls that a heavy-up.
What to do this week
- Write each platform's rules next to its ROAS. In Google Ads, click the Goals icon, open Conversions, select Summary, pick your purchase action and select Edit settings. Note the click-through window and the attribution model. In Ads Manager, open the Columns dropdown next to View Setup, choose Customize columns and add Attribution setting. Pass: both rules sit next to both numbers. Fail: you have been comparing figures built on rules nobody read.
- Take brand search out of Google's ROAS. In Google Ads, select Campaigns, then go to Search terms within the Insights and reports sub-menu. Total the cost and conversion value of searches that contain your brand name. Pass: you know Google's ROAS with and without your own name in it. Fail: brand clicks stay inside the average and prop up every Google figure you hold against Meta.
- Put Meta's cost into GA4. In GA4 Admin, under Data collection and modification, click Data import, then Create import source. Choose Campaign data and select Meta. Then open Advertising, then Planning, then All channels. Pass: Paid Social shows Ads cost and Return on ad spend next to Paid Search. Fail: Meta's cost lands nowhere, so check that your utm_source and utm_medium match the import exactly.
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 attribution models (Google Ads Help); About attribution models and attribution settings (Meta Business Help Center); Results (Meta Business Help Center); Connect Meta to Google Analytics (Google Analytics Help); All channels performance report (Google Analytics Help); About cross-channel budgeting (Google Analytics Help); Implement campaigns for geo experiments (Google Ads Help); Sales reports (Shopify Help Center); About the search terms report (Google Ads Help); About multiple attribution settings (Meta Business Help Center).
Related answers
Frequently asked questions
Should I start with Google or Meta on a small budget?
Usually start where buyers already look. If people search for what you sell, Google search or Shopping can catch that demand first. If nobody searches for it yet, Meta has to create the demand. Either way, give one platform enough budget to read a result before you add the second.Can GA4's cross-channel budgeting split my budget between Google and Meta?
Only if your property has the feature and Meta's cost is imported. Google says it may not be available to every property. Its models count click-through conversions, YouTube engaged views and cost data, so a Meta ad someone only saw gives it nothing to count. Treat its plan as a draft, then test.Should I set one blended ROAS target for Google and Meta?
No. Each platform counts by its own rules, so one target means different things in each report. Set your floor from your margin instead, then judge each platform on the extra sales a regional test shows, not on its own dashboard.
Go deeper: Incrementality testing, explained.
Sixty-second versions of these ideas: Causality Engine on YouTube Shorts.
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Terms in this article
- AttributionAttribution identifies user actions that contribute to a desired outcome and assigns value to each. It reveals which marketing touchpoints drive conversions.
- Attribution ModelAn Attribution Model defines how credit for conversions is assigned to marketing touchpoints. It dictates how marketing channels receive credit for sales.
- ConversionConversion is a specific, desired action a user takes in response to a marketing message, such as a purchase or a sign-up.
- ExperimentsExperiments are scientific procedures that test hypotheses or demonstrate facts. In marketing, experiments like A/B tests determine the causal effect of campaign changes, enabling data-driven decisions.
- First Party DataFirst-Party Data is data collected directly from your audience or customers. This data provides the most valuable insights for marketing.
- Google AnalyticsGoogle Analytics is a web analytics service that tracks and reports website traffic.
- IncrementalityIncrementality measures the true causal impact of a marketing campaign. It quantifies the additional conversions or revenue directly from that activity.
- Incrementality TestingIncrementality Testing measures the additional impact of a marketing campaign. It compares exposed and control groups to determine causal effect.