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Lift and incrementality calculator
Enter the size and conversions of a test group and a holdout group, plus spend, to get lift, incremental conversions, cost per incremental conversion and whether the result is significant.
Lift and incrementality
Enter your numbers to see the result.
Free tool by Telehealth Media · telehealthmedia.com
How it works
A lift test shows ads to one group and holds them back from another. The difference in conversion rates is what the ads actually caused.
- Lift = (test rate - holdout rate) / holdout rate x 100
- Incremental conversions = (test rate - holdout rate) x test group size
- Cost per incremental conversion = spend / incremental conversions
Meta defines conversion lift percent the same way: incremental conversions divided by the conversions it estimates would have happened without the ads (Meta Business Help Center, Conversion lift percent, checked 30 October 2026). The significance line uses the same test as the A/B test calculator.
Worked example
A test group of 200,000 people had 900 conversions; a holdout of 50,000 had 180. Spend on the test group was 30,000 USD.
| Step | Result |
|---|---|
| Test rate | 0.450% |
| Holdout rate | 0.360% |
| Lift | 25.0% |
| Incremental conversions | 180.0 |
| Cost per incremental conversion | 166.67 USD |
These numbers illustrate the formula; enter your own.
Telehealth notes
- Health data limits on Meta make attributed conversions less reliable, which makes holdout tests more valuable.
- Cost per incremental patient is often much higher than reported CPA. That is normal: some patients would have found you anyway.
Questions
What is incrementality?
The share of conversions that happened because of the ads, measured against a group that did not see them.
How big should the holdout be?
Large enough for the difference to be significant. Use the sample size calculator to plan it.
Are my numbers stored?
No. The calculation runs in your browser and nothing is sent to us.