What is a multi-platform ROAS comparator?
A multi-platform ROAS comparator checks the return on ad spend that Meta, Google and TikTok each claim against the revenue that actually landed in your store. This free tool is built for e-commerce brands running ads on two or more channels, the situation where every dashboard looks great but the Shopify or bank numbers don't add up. Enter spend and reported revenue per platform plus your real store revenue, and it returns blended ROAS, true ecosystem ROAS and a 0–100 cross-channel health score.
The core problem it solves is overattribution: when one customer sees your Instagram ad, later clicks a Google Shopping result and buys, both platforms count the same sale.
Why doesn't my platform ROAS match my store revenue?
Each ad platform uses its own attribution window (Meta defaults to 7-day click / 1-day view; Google and TikTok differ again) and each claims full credit for any conversion inside that window. Sum the platform numbers and you double-count. A realistic month for a fashion store:
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| Channel | Spend | Reported revenue | ROAS |
|---|---|---|---|
| Meta | 200,000 | 800,000 | 4.0× |
| 100,000 | 350,000 | 3.5× | |
| TikTok | 50,000 | 120,000 | 2.4× |
| Platforms combined | 350,000 | 1,270,000 | 3.6× |
| Actual store revenue | — | 1,000,000 | 2.9× true |
The platforms collectively claim 1.27M, but the store only made 1.0M, an overattribution factor of 1.27. True ecosystem ROAS is 2.9×, not the 3.6× blended figure the dashboards suggest. Scale budgets on the dashboard number and you'll wonder where the money went.
What is blended ROAS?
Blended ROAS is total platform-reported revenue divided by total ad spend across all channels. It smooths out per-platform attribution quirks but still inherits the double-counting. True ecosystem ROAS (actual store revenue divided by total ad spend) is the number to make budget decisions with. If the two diverge by more than 15%, treat individual platform ROAS claims with suspicion.
Which ad platform has the best ROAS?
For most e-commerce brands Meta still wins on volume and cost, Google Shopping and Search convert high-intent buyers at strong ROAS but limited scale, and TikTok is cheapest per view but weakest on direct attribution. The honest answer is that the mix matters more than the winner, which is exactly why you should measure against store revenue rather than crowning a channel from its own dashboard.
When should I use this tool?
Weekly for active multi-channel campaigns, and always before shifting 20%+ of budget between platforms. Once you know your true ecosystem ROAS, check it clears your break-even ROAS and that the profit math holds in the ad spend ROI calculator. If one channel is underperforming, audit its setup with the campaign health score checker , or browse all free Meta ads tools.
Each platform uses its own attribution window. A single purchase can be counted by Meta and Google simultaneously. Summing platform-reported revenue double-counts conversions. Your true store revenue is the ground truth.
For most e-commerce brands, true ecosystem ROAS above 3× indicates healthy paid acquisition after COGS. Below 1.5× is critical. You may be unprofitable once product costs, shipping, and returns are included.
If platform-reported revenue divided by actual store revenue exceeds 1.15 (15%+ overlap), treat blended platform ROAS with caution.
Use net sales from your backend, after discounts and returns, before COGS. This matches what actually hit your bank account during the same date range as your ad spend.
Weekly for active campaigns, monthly for stable accounts. Run it whenever you consider scaling budgets 20%+, attribution overlap often worsens as you add channels.
Blended ROAS = total platform-reported revenue ÷ total ad spend across all channels. It smooths out per-platform quirks but still inherits double-counting. True ecosystem ROAS (actual store revenue ÷ total ad spend) is the number to use for budget decisions.
For most e-commerce brands, Meta delivers the best combination of scale and cost; Google Search and Shopping convert high-intent buyers at strong ROAS but lower volume; TikTok is cheapest per view but weakest on attribution. Measure all three against real store revenue before picking a winner.