Incremental ROAS calculator
What the ad spend actually drove, measured against a true control. The only honest ROAS.
Inputs
Results
Incremental revenue = Treatment revenue − Control revenue
Revenue the ad caused. Negative or near-zero means the ad mostly cannibalised demand.
iROAS = Incremental revenue / Ad spend
The honest return. Almost always lower than dashboard ROAS by 20-60%.
Lift = (Treatment − Control) / Control × 100
Why this calculator is verified
Incremental ROAS comes from causal-inference work, not from the platform's reported ROAS. Meta's Lift Studies, Google's Conversion Lift, and the academic literature on geo experiments (Vaver & Koehler, Google 2011) all describe the same formula: difference in outcomes between a randomised treatment group and a matched control, divided by the treatment-group spend. This is the only ROAS that survives an audit. Dashboard ROAS always overstates incrementality because it credits cannibalised conversions to the ad.
Worked example
$15K ad spend, $120K test revenue, $95K control
Incremental revenue = $120,000 − $95,000 = $25,000. iROAS = $25,000 / $15,000 = 1.67. Lift = 26.3%. Compare against the dashboard ROAS for the same campaign: if dashboard reports 8.0x but iROAS is 1.67x, the platform is overstating attribution by ~5x. That gap is what kills accounts that scale by chasing dashboard numbers.
Sources for the formula
- Google Research, geo experiments paper (Vaver & Koehler)
The seminal paper. Authoritative source for the methodology.
- Google Ads, Conversion Lift studies
Google's productised version of the same methodology.
- Meta, Conversion Lift
Cross-checks the methodology from Meta's side.
- Andrew Faris, why iROAS exposes platform overcounting
Operator framing of why dashboard ROAS overstates by 20-60% in most accounts.
Related on Ad-Lab
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