How-to · 25 Oct 2026
How to Compare Google Ads and Meta Ads ROAS
Short answer
Compare Google Ads and Meta Ads ROAS on the same date range, the same conversion event and value, and labelled currencies, then note each platform’s attribution window—Meta usually counts view-through sales that Google does not. Read per-platform ROAS (value ÷ spend) beside blended MER (store revenue ÷ total spend) before moving budget.
Last reviewed
A step-by-step way to compare Google Ads and Meta Ads ROAS fairly: same dates, same conversion, matched attribution windows and labelled currencies.
The formulas
- ROAS = conversion value ÷ ad spend. $6,000 of tracked revenue on $2,000 of spend is 3.0.
- MER (marketing efficiency ratio) = total revenue ÷ total ad spend across every channel.
- Break-even ROAS = 1 ÷ gross margin. At a 40% margin you need 2.5 to cover product cost.
Six steps to a fair comparison
1. Use the same date range on both platforms
Read the last 7 and the last 28 days, not a single day. Meta and Google report in the ad account’s time zone, so a midnight cut-off can move a day of sales between platforms if the accounts differ.
2. Count the same conversion with the same value
Pick one event—usually purchase—and make sure both platforms pass the same value (revenue, not a placeholder of 1). If Google counts “add to cart” and Meta counts purchases, the ROAS comparison is meaningless.
3. Check the attribution settings behind each number
Google Ads credits conversions after a click within each conversion action’s window, commonly 30 days. Meta’s default attribution setting typically includes 7-day click and 1-day view. View-through credit makes Meta look stronger on the same sales; note the settings before you judge.
4. Keep currencies labelled
A GBP Google Ads account and a USD Meta account cannot be added together. Convert on purpose with one rate, or compare each in its own currency.
5. Read per-platform ROAS and blended MER together
Per-platform ROAS (conversion value ÷ spend) says where the next dollar should go. MER (total store revenue ÷ total ad spend) checks the platforms are not both claiming the same sale.
6. Move a small slice of budget, then re-read
Shift 10–20% toward the stronger campaigns, wait a full week, and compare the same view again. Look at the biggest spenders first, not only the prettiest ROAS.
Doing it without a spreadsheet
The steps above work in two native UIs and a sheet. Kampalo puts Google Ads and Meta in one dashboard on the same date range, with each account in its own currency, and Kai ranks campaigns on ROAS, CTR and CPC from that snapshot. Solo is $19/month with a 30-day trial and no card.
FAQ
How do you calculate ROAS?
ROAS is conversion value divided by ad spend. $6,000 of tracked revenue on $2,000 of spend is a ROAS of 3.0 (often written 300%). MER uses total store revenue divided by total ad spend across every channel.
What is a good ROAS?
It depends on margin. Break-even ROAS is 1 divided by gross margin: at a 40% margin you need 2.5 just to cover product cost. Compare each platform against your own break-even number, not an industry average.
Why do Google Ads and Meta both claim the same sale?
Each platform credits conversions inside its own attribution window. Meta’s default typically includes 1-day view-through conversions; Google Ads counts conversions after a click within its conversion window. One customer who saw a Meta ad and then clicked a Google ad can be counted by both.
Should I use blended ROAS or per-platform ROAS?
Both. Blended ROAS or MER against real store revenue tells you whether ads pay overall; per-platform ROAS tells you where the next dollar should go. Read them on the same date range.