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Incrementality Lift Calculator
Estimate incremental conversions, incremental ROAS, and incremental profit from a holdout test.
Attribution-reported ROAS can over-credit ads that would have converted anyway. Incrementality asks what lift ads caused compared to a no-ads baseline.
This calculator turns a simple holdout test (exposed vs control) into incremental conversions, incremental ROAS, and incremental profit using AOV and contribution margin assumptions.
Prefer an explanation- Read the guide.
Incrementality lift: how to compute incremental ROAS from holdoutsPaid ads measurement hub: ROAS, MER, marginal ROAS, and incrementalityMarginal ROAS: how to scale ads with diminishing returnsTarget CPA: how to set acquisition targets from LTV and margin
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Tip: you can type commas (e.g., 10,000).
Example
Using the default inputs, the result is:
-$40,400.00
- Exposed users (treatment)
- 100,000
- Exposed conversions
- 1,200
- Holdout users (control)
- 100,000
- Holdout conversions
- 900
- Ad spend (treatment)
- $50,000
- Average order value (AOV)
- $80
- Contribution margin
- 40%
How to calculate
- Enter exposed and holdout sample sizes and conversions.
- Enter ad spend for the exposed group and your AOV + contribution margin.
- Use incremental ROAS and incremental profit to decide what to scale.
Formula
Incremental conversions = exposed_conversions - exposed_users * (holdout_conversions/holdout_users); Incremental ROAS = incremental_revenue / ad_spend
- Holdout group approximates the no-ads baseline for the exposed group.
- AOV and contribution margin are constant for incremental conversions.
- No statistical significance is computed; treat results as directional unless sample sizes are large.
FAQ
Why can incremental ROAS be lower than platform ROAS-
Platforms often claim credit for conversions that would have happened anyway (especially retargeting). Incremental ROAS isolates lift, so it's often lower but more decision-useful.
What if my holdout conversion rate is higher than exposed-
That implies negative lift. It can happen due to noise, non-random assignment, or true cannibalization. Check randomization, sample size, and whether holdout users were truly unexposed.
Common mistakes
- Non-random assignment (exposed users differ from holdout users).
- Too-small samples (results swing due to noise).
- Using revenue but ignoring variable costs (use contribution margin).
Related calculators
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Estimate a target ROAS to cover variable costs plus a desired margin buffer.
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Model CPM -> CTR -> CVR to estimate CPC, CPA, ROAS, and profit per 1,000 impressions (with margin and variable costs).
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ROI Calculator
Calculate Return on Investment (ROI) for a campaign or project.
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Marginal ROAS Calculator
Estimate diminishing returns and find the profit-maximizing ad spend from a simple response curve.
Quick checks
- Keep attribution model and window consistent when comparing campaigns.
- Pair efficiency metrics (ROAS/CPA) with profit assumptions (margin, refunds, fees).
- Validate tracking after site changes (pixels/events can silently break).