Facebook Ads vs Google Ads: what each does best, and how to compare them without the platforms’ arithmetic

Google Ads is strongest where demand already exists — people searching for what you sell — and Meta Ads is strongest at creating demand among people who were not looking, in feeds, stories and reels. Which is better depends on whether people already search for your product, not on which platform reports the higher ROAS. And the reported ROAS cannot settle it anyway: Google Ads uses data-driven attribution by default and reports conversions on the day of the click within a 30-day window, while Meta counts purchases up to 7 days after a click and 1 day after a view, so the same sale can appear in both reports. A fair comparison uses one definition of a sale for both: conversions your store or CRM recorded, each counted once, divided into each platform's spend and tested with incremental budget. Below: how the two differ, why their numbers do not add up, and the comparison that does.

How the two platforms differ

From Google Ads Help on data-driven attribution and conversion reporting, and Meta's help on attribution settings and the learning phase, read September 30, 2026.

Why their reported ROAS cannot be compared

Each platform reports the conversions it gives itself credit for. A customer who clicked a Google Search ad on Monday and saw an Instagram ad on Wednesday before buying is a conversion in both accounts: Google credits it through data-driven attribution within its 30-day click window, Meta through a 1-day view. Add the two conversion counts and the sale is counted twice; compare the two ROAS figures and the channel with the more generous window looks better.

The conversion value behind each ROAS has the same problem, plus its own: Meta says purchases conversion value can include statistically modelled purchases, and both platforms count whatever value the tag sends — usually including tax and shipping, never net of refunds. The conversion value guide goes through each of these.

How to compare them fairly

1. One definition of a sale. Use orders recorded by your store or CRM, each counted once, as the denominator for both platforms. Platform-reported conversions stay useful for optimising inside each platform.
2. Blended numbers first. Total spend on both against total recorded revenue gives blended ROAS — the number no attribution disagreement can move.
3. Marginal, not average. The question is where the next $1,000 goes. Raise one platform's budget for a fixed period while holding the other steady, and watch recorded orders, not platform conversions.
4. Same dates, settled data. Compare periods at least a few weeks old: both platforms keep adding conversions to past days — Meta says its insights stop changing 28 days after they are reported.

Which one to start with

• People already search for your product or category → Google Search first; you are buying intent that exists.
• The product is new, visual or impulse-bought → Meta first; there is little search demand to capture, and creative is the lever.
• Both are running → split budget on marginal cost per recorded order, not on the platforms' own ROAS — the Facebook Ads budget calculator and the Google Ads budget calculator plan each from the conversions you need.

Both platforms on one definition, in one query

TableBI connects Google Ads live and Meta Ads in beta (only people added to its Meta app as test users can authorize until Meta's App Review) into one table where cost, clicks, conversions and conversion value share names, at campaign level. The macros compute ratios over sums, so both platforms' CPA and ROAS use the same arithmetic — the platforms' own attribution still decides what each reports, and the answer's trust block says so.

# Google Ads next to Meta, one definition of CPA and ROAS
tablebi ask "SELECT platform_label(platform) AS channel, SUM(cost) AS spend,
             SUM(conversions) AS conversions,
             cpa(SUM(cost), SUM(conversions)) AS cpa,
             roas(SUM(conversion_value), SUM(cost)) AS roas
   FROM facts WHERE platform IN ('google_ads', 'meta_ads')
     AND date > (SELECT MAX(date) FROM facts) - 28
   GROUP BY platform ORDER BY spend DESC"

FAQ

Related guides

• CPM vs CPC
• What is conversion value?
• Blended ROAS
• One live dashboard for Google Ads and Meta
• Facebook Ads budget calculator
• CPA calculator

Sources

• Google Ads Help — About data-driven attribution
• Google Ads Help — Understand your conversion tracking data
• Google Ads Help — About conversion windows
• Meta Business Help Center — About attribution models and attribution settings
• Meta Business Help Center — About the learning phase
• Meta for Developers — Insights API best practices

npm i -g @tablebi/cli && tablebi install