Definition
Incrementality is the added effect a marketing effort creates: the sales that happened only because the ad ran. Sales you'd have gotten anyway aren't incremental, whatever the platform credits.
Also called: Incrementality, Incremental lift, LiftWhat happened because of the activity?
120 − 100 = 20 additional purchases in the test group. This example does not calculate statistical confidence.
01Define treatment, control and the measurement before starting.
The problem incrementality solves
Retargeting and brand searches look fantastic in attribution — they hit people who were already on their way to buy. But if the customer would have bought regardless, the ad created nothing. It just took the credit.
Incrementality asks: what would have happened without the ad? It's the only question that tells you whether a marketing euro genuinely earns money or just pretties up a dashboard.
How incrementality is measured
The cleanest method is geo-lift or holdout tests: turn the effort off in one group/region, keep it on in another, and measure the difference. Meta and Google also offer built-in conversion lift studies.
From the top down, MER can catch incrementality cheaply: if budget rises and blended efficiency holds, the growth is healthy. If MER falls, you're buying sales you'd have gotten anyway.
How to run a geo-lift test in practice
A geo-lift test is the cleanest test an ordinary e-commerce business can run itself. Split the country (or your markets) into two comparable groups: a test group where the effort runs, and a control group where it's turned off or held flat. Run it long enough for the difference to be statistically credible — typically a couple of weeks to a month depending on volume — and measure the difference in total sales between the groups. That difference is the incremental effect.
The big difference from attribution: you don't have to trust cookies, windows or the platforms' self-reporting. You compare actual revenue in two groups. Meta's Conversion Lift and Google's geo experiments automate some of it, but the principle is the same — hold something back, and measure the difference.
It costs something to switch off working ads in a control group, but it's an investment in knowing what really works. Most brands running their first holdout test discover that some of their “best” attributed channels — retargeting, brand search — are far less incremental than the dashboard claimed.
Frequently asked questions
Why isn't attribution enough?
Attribution allocates the credit for sales that have already happened — it can't know whether the sale would have occurred without the ad. Incrementality measures exactly that difference and is therefore the more honest basis for budget decisions.
Is retargeting incremental?
Often only partly. Some of the customers retargeting reaches would have converted anyway. That doesn't make retargeting worthless, but it means its attributed ROAS overstates the real effect.
From insight to action
See how it applies in practice.
Website, channels and profit measurement
The Løgbutikken engagement covered the website, email, Meta, Google Ads and ProfitMetrics. The business grew and was subsequently acquired.
Read the caseMeasurement and customer economics
Discuss measurement and bidding
We review the values you measure and how they can inform budget decisions.
Choose a time30 minutes · No obligation
About the author
Nicklas Segatz Mortensen
Growth hacker and fractional CMO with 10+ years' experience and hundreds of millions in managed ad spend behind him. Background from larger Danish and international scale-ups, and from the agency world.
Meet the team