What are Incremental Conversions?

  • Incremental conversions measure the additional number of conversions caused by an intervention (treatment) compared to what would have happened without it (control).
  • It’s the extra conversions directly attributable to the campaign, promotion, or treatment — not just the total conversions.

In short:

$\text{Incremental Conversions} = \text{Conversions (Treatment)} – \text{Conversions (Control)}$

Formula

If we split users into treatment (received campaign) and control (no campaign):

$\text{Incremental Conversions} = \Bigg( \frac{y^T}{n^T} – \frac{y^C}{n^C} \Bigg) \times N$

Where:

  • $y^T$ = number of conversions in treatment group
  • $n^T$ = number of users in treatment group
  • $y^C$ = number of conversions in control group
  • $n^C$ = number of users in control group
  • $N$ = total population (users you would target in reality)

This adjusts for baseline conversion rate and scales up to the full population.

Example

Suppose you run a marketing campaign with 10,000 users:

  • Treatment group: 5,000 users → 600 conversions (12%)
  • Control group: 5,000 users → 400 conversions (8%)

Difference in conversion rate:

$12\% – 8\% = 4\%$

Incremental conversions (if all 10,000 users were targeted):

$0.04 \times 10{,}000 = 400$

Interpretation: The campaign generated 400 incremental conversions above what would have happened naturally.

Why is this important?

  • Total conversions can be misleading — some would have converted anyway.
  • Incremental conversions isolate the causal effect of the treatment.
  • This is the foundation of uplift modeling and incrementality testing in marketing, ads, and A/B testing.

Use Cases

  1. Digital marketing: Did the ad campaign actually drive more purchases, or would those users have purchased anyway?
  2. Product experiments: Did a new feature lead to more sign-ups compared to not releasing it?
  3. Healthcare: Did giving a treatment lead to additional recoveries versus natural recovery rate?

Key takeaway:

  • Conversions = everyone who converted, regardless of cause.
  • Incremental conversions = the portion of conversions that only happened because of the intervention.