Yeeyyy your ad campaign generated 1000 conversions. Great news!!!
But what if 800 of those people would have converted anyway?
That’s where the Incrementality Rate comes in. It helps you understand how many conversions your marketing actually really brings in, instead of simply taking credit for conversions that were going to happen anyway.
So, what is Incrementality Rate?
Think about retargeting ads. You show an ad to someone who has already visited your website, browsed your products and maybe even added something to their basket.
If that person ends up buying, did the ad convince them to purchase? Or were they already going to buy it anyway?
Attribution tools might give the ad credit for the conversion.
Incrementality asks a different question: would that conversion have happened without the ad?
How do you calculate it?
Incrementality Rate = (Incremental Conversions ÷ Total Conversions in the Exposed Group) × 100
The goal here is to figure out how many conversions would have happened without the campaign.
Let’s look at an example
Imagine your campaign generates 1000 conversions.
You run a test comparing people who saw your ads with a similar group who didn’t.
The results suggest that 800 conversions would have happened even without the campaign.
That leaves you with 200 additional conversions.
Your Incrementality Rate is: IR = (200 ÷ 1000) × 100 = 20%
In other words, an estimated 20% of the conversions in the exposed group were genuinely incremental.
Why should marketers care?
Because a conversion attributed to your campaign isn’t necessarily a conversion caused by it.
Understanding the difference can help you make smarter budget decisions, question the performance of retargeting campaigns and identify which activities are actually driving additional results.
One thing to keep in mind: you can’t reliably measure incrementality just by looking at campaign reports.
You need a credible comparison, typically using an exposed group and a control group.
The takeaway: don’t just measure how many conversions your ads get credit for. Ask how many they actually generate.
