In the digital era, marketers have never had more data at their fingertips, or more ways to get it wrong. One metric in particular has taken centre stage: Return on Ad Spend (ROAS).
On paper, ROAS looks like the perfect measure of marketing performance: for every pound spent on advertising, how many pounds of revenue came back? Simple. Elegant. Comfortingly precise.
But in reality, ROAS can seduce marketers into a narrow view of success that rewards efficiency over growth.
The Allure and the Limitations
ROAS is popular because it’s easy to calculate and easy to track. It feels like a quick health check for your campaigns. But like all single metrics, it’s only part of the picture.
The cracks show when you start asking deeper questions:
- Does it account for profit? ROAS treats all revenue equally. A campaign driving sales of low-margin products can look “successful” without making you any money.
- Does it prove the ad caused the sale? Attribution models often credit ads for conversions that would have happened anyway, especially when targeting existing customers or brand search.
- Does it measure growth? You can have a high ROAS while market share shrinks if you’re only reaching people who already buy from you.
This is the trap: chasing ROAS can keep you optimising the same audiences, the same channels, and the same tactics — without ever expanding your customer base.
The Growth Gap
What ROAS leaves out is incrementality, the measure of sales that happened because of the advertising, not just during it.
Incrementality is harder to measure and harder to explain in a weekly report, but it’s the closest thing marketing has to a true impact measure. Without it, you’re judging success on what the algorithms say happened, not on the sales you actually created.
High-ROAS campaigns tend to focus on people who are already in-market. They look amazing in-platform but can quietly erode your growth potential. That’s why many brands eventually hit a plateau: the budget is tied up in activity that looks profitable but is mostly skimming sales from loyal customers.
The Case for Broadening the Lens
If you want marketing to drive real growth, you need to look beyond immediate efficiency. That means balancing short-term returns with long-term brand building, and thinking about your spend in three dimensions:
- Across the Funnel – Awareness campaigns often look “inefficient” in ROAS terms but plant the seeds for future demand. Brands that keep feeding the top of the funnel tend to see lower acquisition costs over time.
- Across Channels – Relying too heavily on one or two platforms makes you vulnerable to changing algorithms, competition, or policy shifts. Testing new channels, from emerging social platforms to podcasts to retail media — can unlock audiences you didn’t know you could reach.
- Across Creative – Variety matters. Constantly rotating fresh, distinctive creative gives algorithms more to work with, reaches new segments, and avoids ad fatigue.
From ROAS to Real Impact
If ROAS is your speedometer, think of true ROAS (tROAS) as your sat-nav. It factors in profit, incrementality, and the longer-term value of customers acquired.
You won’t always get perfect data, but you can get closer by running controlled experiments, holdout tests, geo splits, or time-based comparisons — to see how much incremental lift you’re generating.
Often, you’ll find that lower-ROAS channels or campaigns contribute more to long-term growth than their “efficient” counterparts. That broad-reach campaign that never made it into your ROAS leaderboard might be the reason your retargeting works so well.
The Shift That Matters
ROAS still has a place. It’s a useful checkpoint, just not a compass. The real navigational tool is incrementality, asking, “What would have happened if we hadn’t run this campaign?”
Marketers who make this mindset shift:
- Stop optimising purely for immediate efficiency.
- Allocate budget to a healthy mix of short-term conversion and long-term brand building.
- Build resilience into their channel and creative strategies.
Growth doesn’t come from worshipping a single number. It comes from earning attention, building mental availability, and reaching people before they’ve decided to buy.
ROAS can tell you if your engine’s running smoothly. Incrementality tells you if you’re actually heading somewhere worth going.
