Incremental Lift

Incremental lift is the measured increase in conversions, revenue, or another outcome directly attributable to incrementality testing, expressed as a percentage or absolute number.

Incremental ROAS (iROAS) is the incrementality-adjusted version of standard ROAS — instead of dividing all attributed revenue by spend, it divides only the incremental revenue (the portion that wouldn't have happened without the ad) by spend. iROAS is almost always lower than platform-reported ROAS, sometimes dramatically so for channels like branded search or retargeting where a large share of "conversions" would have occurred anyway.

A lift number without a significance test attached is closer to a guess than a finding — at small sample sizes, an apparent 26% lift can be statistically indistinguishable from random noise.