Incremental ROAS (iROAS) Calculator

How do you use this iROAS calculator?

1. Enter Test Spend: Input the exact amount of money spent on the advertising test group.
2. Enter Test Revenue: Input the total revenue generated by the audience exposed to the ads.
3. Enter Control Revenue: Input the total revenue generated by the holdout group (the baseline revenue).
4. Analyze the Output: The tool will instantly calculate your true Incremental Revenue and iROAS multiplier.

Incremental ROAS (iROAS) is the true return on ad spend generated by a marketing campaign, calculated by comparing the revenue of an exposed test group against a holdout control group. Unlike platform-reported ROAS and attribution reporting, which suffer from attribution bias, iROAS isolates the exact revenue that would not have occurred without the ad exposure, providing a CFO-ready metric for budget allocation.

What is iROAS and why is it critical for incrementality testing?

Ad platforms like Meta Ads Manager and Google Ads use last-click or data-driven attribution models that inherently claim credit for organic conversions. Incrementality testing solves this using:

• Randomized Controlled Trials (RCTs) or Synthetic Control Method (SCM): Splitting audiences into exposed and holdout groups.
• Quasi-Experiments: Using methodologies like Geo-testing (e.g., matched market tests) to measure lift.
• Cannibalization Detection: Identifying when branded search ads are simply capturing users who would have purchased organically.

How do you calculate Incremental ROAS?

The formula for iROAS requires isolating the Incremental Revenue and dividing it by the total ad spend for the test group.

• Incremental Revenue = Test Group Revenue – Control Group Revenue
• iROAS = Incremental Revenue / Test Group Ad Spend

Analysts calculating this at scale use SQL in a data warehouse like Snowflake or BigQuery:

SELECT 
    test_spend,
    (test_revenue - control_revenue) AS incremental_revenue,
    (test_revenue - control_revenue) / test_spend AS iROAS
FROM 
    incrementality_experiment_results
WHERE 
    experiment_id = 'Q1_META_HOLDOUT';

Why use iROAS instead of Platform ROAS?