How it works
It shows whether the advertising pays back, but not the profit: an ad account holds no cost of goods. So the same ROAS on products with different markups means a different result for the business, and the only honest comparison is within one category.
Formula
Revenue ÷ spend
Example
A tableware shop: spend 40,000, revenue 180,000.
ROAS = 180,000 ÷ 40,000 = 4.5. For every unit put in, 4.5 came back.