Google Ads vs Meta Ads ROAS: Why They Differ and How to Compare Them

Google Ads says ROAS is 3.5. Meta says 2.8. Your store says you made less than both claim. All three can be right, because each one counts a different thing.

By Published Updated 8 min read
On this page
  1. The formula
  2. Where each platform gets it
  3. Why the numbers differ
  4. How to compare fairly
  5. A worked example
  6. Doing it in Better Analyst
  7. FAQ

The short answer

ROAS is conversion value divided by ad spend. Google Ads and Meta Ads calculate it from their own attributed conversions, using different attribution rules, so the two numbers are not directly comparable and usually add up to more revenue than you earned. Compare each platform against your break-even ROAS, track trends rather than absolute values, and check both against one revenue source you trust, such as GA4 or your order data.

Build a ROAS dashboard

The formula

ROAS = attributed conversion value ÷ ad spend, for the same campaigns and the same dates. A ROAS of 4 means each dollar of spend was credited with four dollars of conversion value.

ROAS is not profit. To break even on the first order, ROAS has to cover your cost of goods, so break-even ROAS = 1 ÷ gross margin. At a 40% margin that is 2.5; at 25% it is 4. A campaign at 3.0 is profitable for the first business and losing money for the second.

Where each platform gets its number

Google Ads reports conversion value (metrics.conversions_value) and cost (metrics.cost_micros, in millionths of the account currency). ROAS is conversion value divided by cost after converting micros. Which conversion actions count, and how credit is assigned, is set on each conversion action in the account.

Meta Ads reports spend and the value of actions such as purchases (action_values), plus a ready-made purchase_roas. Credit follows the ad account's attribution setting, which can include conversions after someone saw an ad without clicking it.

Both platforms report in the ad account's currency and time zone. If your Google Ads account runs in New York time and your Meta account in London time, "yesterday" covers different hours.

Why the numbers differ

  1. Step 1Different attribution rulesEach platform decides which touch gets credit and for how long after the click or view. Longer windows and view-through credit raise reported ROAS.
  2. Step 2Double countingA customer who clicks a Google ad and saw a Meta ad can be counted as a conversion by both platforms. Platform totals can exceed real revenue.
  3. Step 3Different conversion definitionsOne account may count purchases only; another may include leads or add-to-carts with assigned values. Check what is in the value.
  4. Step 4Modeled conversionsPlatforms estimate some conversions they cannot observe directly, so reported values can change after the fact.
  5. Step 5Currency and time zoneAccounts in different currencies or time zones need converting before you add or compare them.
  6. Step 6Different jobsSearch usually captures existing demand; social often creates it. A lower ROAS on Meta can still feed sales that Google Ads later claims.

How to compare them fairly

  1. Pick one revenue source of truth. Use GA4 or your order data for total revenue, and treat platform ROAS as each platform's view of its own contribution.
  2. Report blended ROAS next to platform ROAS. Blended ROAS (your revenue ÷ total ad spend) cannot double count. Platform ROAS tells you where to look.
  3. Compare against break-even, not against each other. Each platform should clear your break-even ROAS on the conversions it claims.
  4. Watch trends. A platform's ROAS moving from 3.5 to 2.9 over a month is a clearer signal than the gap between two platforms on any one day.
  5. Keep the spend in view. A ROAS of 9 on $50 of spend tells you little. Rank campaigns with a minimum spend.
  6. Test when the stakes are high. Before moving a large budget, run a holdout or geo test to measure what each channel adds beyond what it claims.

A worked example

An illustrative month for a store with a 40% gross margin (break-even ROAS 2.5):

Illustrative ROAS by platform compared with blended ROAS
SourceSpendConversion valueROAS
Google Ads$6,000$21,0003.5
Meta Ads$4,000$11,2002.8
Platforms combined$10,000$32,2003.2
Store orders (blended)$10,000$26,0002.6

The platforms claim $32,200 between them, but the store recorded $26,000, so about $6,200 was claimed twice or attributed generously. Both platforms clear break-even on their own numbers. The blended ROAS of 2.6 is only just above 2.5, which is the number that decides whether the month made money. Before adding budget, check whether Meta's 2.8 holds up against store orders for the customers it reached.

Doing it in Better Analyst

Connect Google Ads, plus GA4 or the database your orders live in. The Meta Ads connector is coming soon; once it is available, you will be able to ask:

  • "Show spend, conversion value and ROAS by week for Google Ads and Meta Ads this quarter, plus blended ROAS from GA4 purchase revenue."
  • "Which campaigns on either platform are below a break-even ROAS of 2.5 with at least $500 of spend last month?"
  • "Compare Meta-reported purchases with GA4 purchases attributed to paid social by week."

Each answer shows the queries and the code that joined them, so you can check that micros were converted and dates line up. Turn the result into a ROAS dashboard, or read how to analyze Google Ads data with AI for more questions to ask.

Check Google Ads ROAS against your real revenue

Connect Google Ads and your revenue source today, then ask for ROAS by channel, campaign and week with the formula shown. Meta Ads is coming soon.

Try Better Analyst freeBook a demo

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ROAS is attributed conversion value divided by ad spend for the same period. $8,000 of conversion value on $2,000 of spend is a ROAS of 4, sometimes written 400% or 4:1.
There is no general answer. Search ads often reach people who are already looking to buy, while Meta ads often reach people earlier, so the platforms do different jobs. Compare each against your own break-even ROAS and against the same revenue source rather than against each other.
Each ad platform credits conversions using its own attribution rules and windows, and can count conversions on other devices or after an ad view. GA4 and your store count orders their own way. The same order can be claimed by both platforms, so platform totals often add up to more than your real revenue.
One that is above your break-even ROAS, which is 1 divided by your gross margin. At a 40% margin, break-even is 2.5: below that, the ads lose money on the first order.
Total revenue from your own records divided by total ad spend across every platform. It ignores which platform claimed the sale, so it cannot double count, but it also cannot tell you which channel to cut.

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