Prime Day 2025: A Unified Measurement Playbook for Retail Marketers

Prime Day 2025 is shaping up to be one of the year’s biggest shopping events – and a high-stakes moment for retail marketers. Amazon has extended Prime Day to a four-day affair (July 8–11, 2025), the longest in the event’s history. Billions of dollars will be spent not only on Amazon but across other retailers running competing sales. Last year’s Prime Day saw record-breaking online sales (an estimated $14.2 billion, up 11% YoY). In short, everyone is raising their bets – and noise in the data will rise with it. 

The stakes are high—but so is the risk of misjudging what’s really driving performance. With multiple platforms all reporting their own version of success, siloed metrics often distort reality. ROAS looks inflated, conversions appear duplicated, and teams struggle to understand how their spend on TikTok, Meta, or YouTube impacts revenue across both .com and marketplaces like Amazon. 

This blog post will help you cut through that noise by focusing on three key opportunities: 

• Understanding how DTC media impacts Amazon sales 

• Adopting Unified Metrics for agile optimisation during Prime Day 
• Evaluating total revenue impact, not just siloed channel ROAS 
  
  

 1. DTC-focused paid media campaigns drive Amazon sales

Fragmented measurement has long hidden the impact of cross-channel investment—but the data is now clear. Fospha research shows that 42% of Amazon sales are influenced by non-Amazon paid media, with upper-funnel campaigns on TikTok, Meta, YouTube, Snap and Demand Gen playing a major role. 

This matters because most brands still optimise media channels in isolation. If you’re only measuring ROAS on your DTC site, you’re likely underinvesting in the very platforms that are generating demand you later capture on Amazon. 

That’s where Unified ROAS (uROAS) comes in. It gives brands a single metric to evaluate true performance across both DTC and Amazon. The uplift is significant: 

• TikTok’s uROAS is 80% higher than its DTC-only ROAS 

• YouTube sees a 48% uplift 

• Meta delivers a 46% increase 

These halo effects quantify the value of brand-building and upper-funnel activity—not just in driving direct conversions, but in influencing purchase behaviour on Amazon. Relying on pixel-based MTA or siloed reports will miss this impact completely, leading to wasted opportunity and flawed budget decisions.

2. Unified Metrics only work when teams are set up to act on them

Seeing the full picture is only step one. Winning brands are those who are set up to act on Unified Metrics in real time. 

Nécessaire shows what’s possible when strategy and structure are aligned. With clear evidence that TikTok and Meta were driving not just DTC sales but significant Amazon conversions, they doubled down on upper-funnel investment ahead of Prime Day. The payoff? 

• 47% higher Prime Day revenue vs. benchmark 

• 65% of Amazon conversions were organic, indicating that demand was successfully generated upstream 

But not every brand is operationally ready to move like this. Unified metrics often reveal deeper organisational blockers: 

• Budgeting silos mean teams undervalue campaigns that look inefficient in DTC-only dashboards, even when they’re powering Amazon sales 

• Channel team fragmentation leads to competing KPIs, missed synergies, and a lack of ownership over total eCommerce growth 

To succeed with uROAS, brands must unify not just their data—but their strategy: 

• Align goals and KPIs across .com and marketplace teams 

• Break down reporting silos to support cross-channel optimisation 

• Empower decision-makers with real-time insights, not retrospective analysis 

Great measurement is only as valuable as your ability to act on it. And during Prime Day, agility is everything. 

3.Understand which channels drive incremental sales—and which cannibalize

Prime Day isn’t just about high ROAS—it’s about total revenue growth. And the only way to know whether your media is driving incremental sales or just shifting demand between channels is to look at performance through a unified lens. 

Siloed metrics create a false sense of success. One platform reports a strong ROAS, another claims the same conversion, and your team ends up scaling campaigns that aren’t actually growing the pie. 

With Fospha’s Unified ROAS, you can see what’s truly additive. For example: 

• TikTok’s Unified ROAS doubled when Amazon revenue was included 

• Meta’s rose by 87% 

• Google Demand Gen showed a 41% uplift, proving its role in mid-funnel influence 

You can’t make these decisions if you’re just comparing DTC dashboards. You need one view across all revenue streams—so you know which channels deserve more budget, and which are just cannibalising results elsewhere. 

4. Don’t ignore Amazon Ads—they matter too

While understanding halo effects is essential, Amazon Ads still play a critical role. In fact, Nécessaire’s performance wasn’t just a function of Meta and TikTok success—it was also driven by strategic investment in Amazon itself. 

Fospha’s data shows that Nécessaire had a 37% Share of Wallet (SOW) on Amazon Ads during Prime Day—the highest among our beta group. This high SOW gave Nécessaire strong visibility and Buy Box wins, enabling them to capture demand efficiently once it had been generated by upper-funnel campaigns. 

The takeaway? Brands should: 

• Continue to invest in Amazon Ads, especially during high-intent moments like Prime Day 

• Use uROAS to coordinate Amazon and non-Amazon spend, ensuring both demand generation and capture are optimised 

• Avoid over-relying on just one channel’s performance view—Amazon Ads need to be measured in context 

Unified measurement isn’t about replacing Amazon Ads—it’s about ensuring they’re part of a joined-up, full-funnel strategy. 

Conclusion: Turn Measurement into Your Prime Day Advantage 

Prime Day is a sprint and a marathon all at once – a whirlwind few days that can define your Q3 results, and offer lessons that carry into Q4’s holiday push. The brands that come out on top aren’t necessarily the ones who simply spend the most; they’re the ones who measure the smartest. In the crucial lead-up and the frantic live hours of Prime Day, accurate and unified measurement is your secret weapon. It cuts through misleading signals, shows you where the real opportunities are, and gives you the confidence to double down on what works (and trim what doesn’t) in real time. 

In 2025’s Prime Day, the stakes are higher and the window is longer – meaning more chances to win big, but also more chances to waste money if you’re flying blind. By adopting a unified metrics approach, you ensure that you’re not just collecting data, but truly understanding performance across your entire marketing ecosystem. You’ll know which campaigns are driving incremental growth, how each platform is actually contributing to the bottom line, and where to push for maximum impact. When your metrics are unified and predictive, your team can operate with the agility and insight that this high-speed event demands. 

So as you finalize your Prime Day game plan, ask yourself: will we merely report on what happened after the fact, or will we leverage unified measurement to inform what we do as it’s happening? The latter is how you capture the full value of Prime Day. This Prime Day, don’t just measure what happened. Know what’s working — and scale it while it’s still happening.