Return on ad spend compares revenue attributed to advertising with the amount spent on those ads.
How it works in retail
ROAS equals attributed revenue divided by ad spend. It may be expressed as a ratio, multiple or percentage, such as 4:1, 4× or 400%.
A retail example
A campaign is attributed $8,000 in revenue on $2,000 of ad spend. Its reported ROAS is 4×.
What to keep in mind
ROAS does not deduct product costs, fulfillment, returns or overhead. Different attribution rules and revenue definitions can produce different figures for the same campaign.
Sources & further reading
Google Ads: Campaign performance measures
Examples are illustrative. Terminology and measurement conventions can vary by business and market.