Let's do some math that might ruin your morning.
You're running a Shopify store. Meta Ads Manager says your ROAS is 4.2x. Google Ads says 3.8x. You're spending $5,000 on Meta and $3,000 on Google — $8,000 total. According to the platforms, you're generating $35,400 in revenue from that spend.
But your Shopify dashboard shows $28,000 in total revenue for the period. Not all of it came from ads — some was organic, some was email, some was direct. So where's the other $7,400 that the platforms claim they drove?
It doesn't exist. It's the gap between reported and real.
The three inflation engines
Your ROAS is inflated by three mechanisms working simultaneously. Understanding each one is the first step to seeing your real numbers.
Inflation source #1: Brand cannibalization
Your Google Ads account probably has a brand search campaign. It bids on your store name and branded terms. Its ROAS looks incredible — maybe 8x or 10x.
But think about what's happening. Someone types your brand name into Google. They already know who you are. They were coming to your store regardless. Google places your ad at the top, they click it instead of the organic result, and Google charges you $1.50 for a customer who was already yours.
Google reports this as a conversion. Your ROAS number goes up. Your actual incremental revenue from that click? Likely zero.
How much of your brand spend is cannibalized depends on your brand strength, but estimates typically range from 40–70% for established Shopify stores. If you're spending $1,000/month on brand search and 50% is cannibalized, that's $500/month inflating your ROAS without driving real revenue.
Inflation source #2: Creative fatigue
This one is subtler. Your ads don't suddenly stop working — they fade. An ad that launched at 2.5% CTR three weeks ago might be at 1.4% today. It's still generating some clicks, some conversions. But the cost per conversion has nearly doubled.
The reported ROAS doesn't capture this degradation clearly. Meta shows you total conversions and total spend, but it doesn't say, "Hey, this creative is 44% less efficient than it was at peak and you should probably replace it."
That efficiency gap — the difference between what the ad could be doing and what it is doing — is a form of waste. It's money spent on diminishing returns. And because the creative is technically still "working," most merchants never notice.
Over a portfolio of 10 active creatives, if the average efficiency decline is 25%, your effective ROAS is 25% lower than reported. Check your own creatives with our Creative Fatigue Checker.
Inflation source #3: Channel overlap
This is the most mechanical and easiest to understand.
A customer sees your Meta ad on Monday. On Wednesday, they Google your brand name, click a Google ad, and buy. Meta reports a conversion (7-day click window). Google reports a conversion (same order, attributed to the search click). Your Shopify store records one order.
Two platform conversions. One actual sale. Your combined reported revenue is 2x reality.
This isn't rare. It's the default. Any merchant running both Meta and Google is experiencing some degree of overlap. The typical range is 15–40% of total reported conversions, depending on spend levels and audience overlap.
A worked example: from 4.2x to 2.1x
Let's trace the full inflation for a real scenario.
Starting point: $8,000 monthly spend. Reported blended ROAS: 4.0x. Reported revenue: $32,000.
After removing cannibalization: Brand search is $1,500 of Google spend. Estimated 60% cannibalized = $900 in non-incremental spend. Adjusted revenue drops by ~$7,200 (the inflated conversions from those clicks). New effective revenue: $24,800.
After removing fatigue waste: Average creative efficiency decline across the portfolio: 20%. That means 20% of non-brand spend ($6,500 × 0.20 = $1,300) is buying diminished conversions. Revenue generated per dollar is lower than reported. Adjusted effective revenue: ~$22,200.
After removing overlap: 25% of total conversions are double-counted between platforms. Adjusted effective revenue: ~$16,650.
True blended ROAS: $16,650 ÷ $8,000 = 2.1x
That's half the reported number. And it's a conservative estimate — actual overlap and cannibalization rates can be higher.
Want to see your own numbers? Our True ROAS Calculator lets you plug in your actual spend and ROAS to see the estimated gap.
Why the platforms don't fix this
Meta and Google aren't trying to mislead you. They're both doing exactly what their attribution models are designed to do: take credit for conversions within their attribution windows.
The problem is structural, not malicious:
Each platform only sees its own data. Meta doesn't know about your Google clicks, and Google doesn't know about your Meta impressions. Neither can detect overlap because neither has the other's data.
Attribution windows are generous by default. Meta's default 7-day click window means any purchase within a week of clicking a Meta ad gets attributed to Meta — even if the customer found you through a Google search the day they bought.
No platform has an incentive to show lower numbers. Reporting fewer conversions would mean merchants spend less on their platform. The structural incentive is always toward more claimed conversions, not fewer.
This doesn't make the platforms useless. Their targeting, creative tools, and reach are genuinely valuable. But their reporting should be read as "potential conversions influenced" rather than "conversions caused."
How to find your true ROAS
There are three levels of accuracy, each requiring more effort:
Level 1: Estimate (5 minutes). Use our True ROAS Calculator. Plug in your reported ROAS, spend per platform, and brand search percentage. You'll get an estimated range. This uses industry averages — it's directionally correct but not precise for your store.
Level 2: Analyze (connect your data). Connect your actual Shopify, Meta, and Google data to an analytics tool that cross-references conversions across platforms. This reveals your specific overlap rate, your actual creative fatigue levels, and your store-specific cannibalization signals. The output is an audit with confidence-rated findings.
Level 3: Prove (run an experiment). The only way to know your true ROAS with certainty is to run a holdout experiment. Temporarily pause ads for a portion of your audience. Measure the actual revenue impact. If revenue barely changes, those ads weren't incrementally valuable. If it drops proportionally, they were. Learn more in our guide to holdout experiments.
The uncomfortable truth
Knowing your true ROAS is uncomfortable. A merchant who believed they had 4x ROAS learning they actually have 2x ROAS might feel like they've been doing something wrong. They haven't. They've been working with the numbers they were given.
The question isn't whether your ROAS is inflated — for most merchants running both Meta and Google, it is. The question is what you do about it. Some merchants would rather not know. They prefer the comfortable dashboard numbers.
But the merchants who face the real numbers — and optimize against them — end up spending less and making more. Because once you know which 29% of your spend is waste, you can reallocate it to the campaigns and creatives that actually drive incremental revenue.
That's the gap between reported ROAS and real profit.