ROAS (Return on Ad Spend)

Revenue generated for every unit of advertising spend. Calculated as: Revenue ÷ Ad Spend. The most widely used media efficiency metric in eCommerce, though it comes with an important caveat: ROAS derived from platform or pixel data is subject to attribution bias, and channels can be both over- and under-credited depending on where they sit in the funnel. MMM-derived ROAS provides a more accurate, causal estimate.