Blended ROAS
Blended ROAS is return on ad spend calculated from total revenue and total advertising cost across all channels at once. No conversion crediting, no platform reports: revenue from the books, spend from the invoices. It shows the company's reality instead of the sum of each platform's optimistic numbers, which is routinely higher than actual revenue.
In short
| Formula | Blended ROAS = total revenue / total ad spend |
| How it differs from MER | Practically not at all. MER usually counts all marketing costs, blended ROAS only ad spend |
| Why it exists | Platforms credit each other's conversions. The sum of their ROAS figures is fiction |
| How it is used | As a trend over time and a sanity check on platform numbers, not as a campaign metric |
How it is calculated
Inputs and steps
The calculation has four steps, and all of them rest on data outside the ad platforms.
- Period. A calendar month. Revenue and spend are taken for the same calendar month; otherwise the number swings.
- Revenue. All orders for the month from the order system or the books, excluding VAT, net of cancellations and returns. No filtering by source: organic, direct and email revenue all belong in it.
- Spend. Spend from every ad platform, excluding VAT, with brand and awareness campaigns included. Agency fees, tools and production stay out; adding them turns the metric into MER.
- Ratio. Revenue divided by spend. The result is one number for the whole company. Both sides without VAT: revenue including VAT against spend excluding it overstates the result by the full VAT rate.
Worked example
Worked example: an online store books €240,000 in monthly revenue excluding VAT, net of cancellations. Ad spend: Google Ads €30,000, Meta €24,000, TikTok €6,000, a total of €60,000.
| Total revenue | €240,000 |
| Total ad spend | €60,000 |
| Blended ROAS | 240,000 / 60,000 = 4.0 |
| Revenue credited by the platforms | 138,000 + 108,000 + 15,000 = €261,000 |
| Summed platform ROAS | 261,000 / 60,000 = 4.35 |
For the same month the platforms credited themselves with €261,000, which is more than the store's entire revenue including organic and email. The gap between 4.35 and 4.0 is the sum of double counting and modeled conversions; the blended figure, in turn, contains revenue that no platform claims. The two numbers therefore measure different things, and the gap between them is a diagnostic, not an error.
How to read the result
The value 4.0 says nothing on its own until it is set against the break-even point. That point comes from margin: at a 30% contribution margin the break-even blended ROAS is 1 / 0.30 = 3.33. A blended ROAS of 4.0 therefore means advertising as a whole makes money; at 3.0 it would not pay for itself. The second use is the trend: when spend grows month over month and blended ROAS falls, each additional euro brings back less than the previous one. What the number cannot do: say how much revenue would have arrived without any advertising. That is what incrementality tests are for. And the definition stays the same month after month: changing the method mid-year destroys the trend, which is the main reason blended ROAS is tracked in the first place.
Why platform ROAS overstates and blended does not
A worked example: Meta reports conversions worth 80,000, Google reports 90,000, but total revenue for the same period is 120,000, because a share of the purchases got credited by both platforms at once. At 40,000 of spend the platforms jointly report a ROAS of 4.25, while blended ROAS is 3.0. The gap is not a measurement error, it is double counting. The more channels run, the bigger the gap tends to be, and the more important it is to keep one number next to the platform figures that matches the bank account.
From our own practice
For multi-channel clients, together more than EUR 52 million of managed spend, we always keep two-layer reporting: platform metrics for daily steering, the blended view for the monthly review. As a rule we never compare Meta pixel data one to one with GA4 and never sum CPA across channels, because every system measures differently and the sum always comes out prettier than reality. Blended ROAS is the anchor that keeps the whole reporting grounded.
Common mistakes
- Summing platform ROAS. The sum of credited conversions exceeds real revenue. Always.
- Steering campaigns with it. A blended number cannot say which campaign works. That is what campaign metrics and tests are for.
- Ignoring margin. Revenue-based blended ROAS has the same blindness as ordinary ROAS. The full picture needs margin, see POAS.
Related terms
See also MER, POAS, ROAS, incrementality and attribution model.
Frequently asked questions
Why does blended ROAS differ from the platform numbers?
Because platforms credit while blended counts. The gap is the amount of double counting and modeled conversions. The bigger the gap, the more the channels are claiming each other's results.
How often should it be calculated?
Monthly is enough. Daily values fluctuate because revenue and spend are not synchronous.
Do brand campaigns belong in it?
Yes. That is exactly what makes the blended view useful: it captures the effect of campaigns that never claim conversions.
How we can help
We build two-layer reporting from platform numbers to company reality as part of our Performance marketing agency service.