Advertising and marketing metrics
ROAS (return on ad spend)
Revenue attributed to ads divided by ad spend. It ignores product cost, shipping and returns, so two campaigns with the same ROAS can have very different profit.
ROAS is revenue attributed to ads divided by ad spend. It is the number every ad platform reports natively, which makes it the most common way to compare campaigns and the first metric an assistant will pull when asked how ads are doing.
Its weakness is that revenue is not profit. ROAS ignores product cost, shipping, payment fees and returns, so two campaigns with the same ROAS can contribute very different amounts to the business. It also depends on the platform's own attribution, which counts conversions differently from your store and from other platforms, so ROAS figures from several channels rarely add up to what you actually sold.
ROAS is still useful as a relative signal within one platform, and as the metric the platform's bidding understands. When you ask an assistant for ROAS, ask in the same breath for the attribution window and for a profit-based figure such as POAS where cost data is available, so the comparison is not misleading.