iROAS calculator
Calculate incremental ROAS from randomized test and control groups, or enter an existing incremental revenue estimate. Compare the result with your contribution margin and download the calculation. Use the same period, audience and currency throughout.
Prefilled numbers are a fictional example. Use one currency, audience and period. Revenue includes everyone assigned to each group, including people who never saw an ad. Amounts exclude tax and use a consistent refund policy.
For randomized individuals with comparable follow-up. Regional holdouts need a geo-specific analysis; population scaling alone cannot correct differences between regions.
- Estimated incremental revenue
- 5,600
- Estimated iROAS
- 0.70x
- Platform ROAS
- 4.20x
- Incrementality factor
- 16.7%
- Break-even revenue iROAS
- 1.67x
- Incremental contribution after ads
- -4,640
Test revenue per person: 3.36. Control: 2.8. Expected test-group revenue without treatment: 28,000. Relative revenue lift: 20.0%. Incremental share of test revenue: 16.7%.
The point estimate does not cover ad spend after the variable costs included in the margin. Additional marketing costs and fixed overhead are excluded. This is not a recommendation to change your budget.
These totals cannot establish statistical significance or a confidence interval. Review assignment, contamination, outcome variance and your pre-agreed decision rule. The incrementality factor compares an experimental estimate with attributed revenue; it does not prove a platform error.
CSV saves your current values. The Excel workbook starts with the fictional example and includes formulas and a test-plan template.
How to calculate incremental ROAS
iROAS = estimated incremental revenue ÷ ad spend. The incrementality factor is incremental revenue ÷ platform-attributed revenue. Revenue-based break-even iROAS is 1 ÷ contribution margin before ads, expressed as a decimal.
In the example, $5,600 ÷ $8,000 = 0.70x iROAS. At a 60% contribution margin, break-even is 1.67x. Incremental contribution after ads is $5,600 × 60% − $8,000 = −$4,640.
For unequal randomized groups, estimated incremental revenue = test revenue − (control revenue ÷ control group size) × test group size. Using revenue per assigned person allows order values to differ between groups. Follow the holdout calculation and spreadsheet formulas. This calculator does not estimate statistical significance or validate the experiment.
The free incrementality test template includes an editable plan and the same example in Excel. CSV export saves your current calculator inputs and results; the Excel download starts with the fictional example.
What counts as a good iROAS?
There is no universal threshold. A 40% contribution margin implies 2.50x revenue iROAS to cover ad spend; a 60% margin implies about 1.67x. Include creative, agency fees and other relevant costs when calculating marketing ROI.
Can iROAS be negative or the factor exceed 100%?
Yes. A negative effect estimate produces negative iROAS. A factor above 100% means the test estimates more incremental revenue than the platform attributes. Check scope, timing and uncertainty before interpreting either result.
What the incrementality factor is for
You cannot run a test every week, but you look at platform dashboards every day. The factor bridges the two: multiply platform-reported revenue by the factor to get a rough estimate between tests, provided the audience, spend and measurement conditions remain comparable. Carry forward the uncertainty of the original test. Background: what is iROAS and the incrementality testing guide.