Incremental ROAS (iROAS)
Incremental ROAS (iROAS) is revenue that would not have happened without the ad, divided by the ad spend. It counts only the lift a channel causes, unlike platform ROAS, which credits conversions that may have happened anyway.
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By Joris van Huët, Founder & CEOUpdated 2 min read
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What is Incremental ROAS (iROAS)?
Platform-reported ROAS assigns credit by clicks and views; incremental ROAS is measured causally, by comparing outcomes against the would-have-happened-anyway baseline. No pixel required.
Why Incremental ROAS (iROAS) matters for ecommerce
Budgeting on platform ROAS systematically overfunds channels that harvest existing demand.
Frequently asked questions
What is incremental ROAS (iROAS)?
Incremental ROAS is revenue that would not have happened without the ad, divided by the ad spend. It counts only the lift a channel causes, unlike platform-reported ROAS, which credits conversions that may have happened anyway.Why is incremental ROAS usually lower than platform ROAS?
Because platforms self-attribute: they claim credit for any conversion their ad touched, including purchases from customers who would have bought regardless, such as branded-search clicks and retargeted existing customers. Stripping out those would-have-happened-anyway conversions leaves only the caused revenue, which is a smaller number.How is incremental ROAS calculated?
The formula is: Incremental ROAS = (Revenue with the channel minus Revenue without the channel) divided by channel spend. The hard part is estimating the counterfactual, the revenue without the channel, which is done with holdout experiments or causal inference on your existing analytics data.