Are your Google Ads creating revenue, or just recording it?
Most ecommerce accounts overstate their Google Ads contribution by 30-50%. Brand searches, organic cannibalisation, and repeat customers inflate the numbers. Incremental revenue is what remains when you strip out the traffic you would have received anyway.
The cannibalisation problem nobody talks about.
Google Ads reports every conversion it touches. It does not tell you which conversions would have happened without the ad. When your brand campaign shows 12x ROAS, it is not because the campaign is exceptional. It is because those customers were already searching for you by name.
The real question is not "how much revenue did Google Ads generate?" It is "how much revenue would we have lost without it?"
Brand campaigns claiming 40%+ of conversions
If branded search is your biggest converter, your ads are recording demand, not creating it. Those customers were coming anyway.
Organic revenue drops when paid spend increases
A classic cannibalisation signal. You are paying to steal from yourself.
High ROAS but flat overall revenue
The campaign looks efficient because it is harvesting existing demand. But total business revenue has not moved. The 'growth' is an accounting illusion.
New customer rate declining despite rising spend
You are spending more to reach fewer new people. The algorithm is re-targeting existing customers because they convert easily, inflating your metrics.
Shopping ads appearing for searches you rank #1 organically
You are paying for clicks you would have received for free. Every one of these is a margin leak.
How we measure what matters.
Five steps to separate real growth from attribution theatre.
Isolate brand from non-brand
Separate branded search from everything else. Brand traffic is demand you already own. Non-brand is where incremental growth lives.
Run geo holdout tests
Pause ads in a representative region for 2-4 weeks. Measure the actual revenue difference, not the forecasted loss. This is the gold standard for proving incrementality.
Measure new vs returning customer split
If 70% of your Google Ads conversions are existing customers, your campaign is a retention tool, not an acquisition tool. Price it accordingly.
Calculate contribution margin per new customer
Revenue minus COGS, shipping, returns risk, payment fees, and ad cost. If this number is negative, your 'profitable' campaign is losing money on every new customer.
Compare to organic baseline
What would revenue be with zero Google Ads? The difference is your true incremental contribution. Everything above that baseline is what you are actually paying for.
What the maths actually looks like.
Reported Google Ads revenue
£200,000/month
Minus: branded search (customers already searching for you)
-£80,000
Minus: cannibalised organic (would have clicked organic listing)
-£30,000
Minus: returning customers (coming back regardless)
-£25,000
True incremental revenue
£65,000/month
The campaign is not 10x ROAS. It is 3.25x incremental ROAS. Still positive, but scaling based on the inflated number will destroy margin.
Related thinking.
Questions about incrementality.
What is incremental revenue in PPC?
Incremental revenue is the revenue generated by Google Ads that would not have occurred without the ad spend. It excludes brand searches from existing customers, cannibalised organic traffic, and retargeted visitors who were already coming back. Most accounts overstate their contribution by 30-50% because they count all conversions, not just incremental ones.
How do you measure incrementality without a massive budget?
Geo holdout testing is the most accessible method. Pause ads in one region for 2-4 weeks and compare total revenue (not just ad revenue) against a control region. This gives you directional truth without needing a data science team. We run these tests quarterly for every client.
Why do most agencies not measure incrementality?
Because the results often show that campaigns are less effective than platform metrics suggest. Measuring incrementality honestly can reduce the perceived value of the agency's work. We measure it because understanding true contribution is the only way to make smart scaling decisions.
What is the difference between ROAS and incremental ROAS?
ROAS measures total revenue attributed to ads divided by ad spend. Incremental ROAS measures only the additional revenue that would not have happened without the ads. A campaign can show 8x ROAS but 2x incremental ROAS if most of the attributed revenue would have occurred organically.
How does incrementality relate to POAS?
POAS (Profit on Ad Spend) measures profit per ad pound. Incremental POAS goes further: it measures the profit from revenue that only exists because of the ad spend. Combining both gives you the clearest picture of whether scaling spend will actually grow profit, not just move it around.
How we work
See allFind out what your ads actually contribute.
We will show you the gap between reported and incremental revenue in your account. No charge. No obligation. Just the truth.
Book an incrementality audit