How to calculate blended ROAS across Meta, Google, TikTok, and Amazon
Add revenue across the selected channels, add spend across the same channels, then divide the two totals. Do not average channel ROAS values directly because channels with very different budgets would receive equal weight.
For example, a 5.0x channel on $1,000 spend produces $5,000 revenue, while a 2.0x channel on $10,000 produces $20,000. Combined revenue is $25,000 on $11,000 spend, so blended ROAS is 2.27x, not the 3.50x simple average.
Review the weighted ROAS formula
Blended ROAS = total attributed revenue ÷ total advertising spendHow to align attribution windows before blending ROAS
Use the same reporting dates, currency, conversion event, and revenue basis for every row. Check whether each platform reports by click date or conversion date, includes view-through conversions, models conversions, or keeps refunds and taxes in conversion value.
When settings cannot be aligned, disclose the mismatch beside the result and avoid treating the total as a precise source of truth. A weighted calculation fixes the arithmetic, but it cannot deduplicate one order claimed by multiple platforms or prove that attributed revenue was incremental.
Blended ROAS vs marketing efficiency ratio (MER)
Blended ROAS usually combines attributed revenue from selected paid channels. MER often divides total business revenue by total marketing spend. The metrics can look similar but answer different questions, especially when organic, direct, email, retail, and repeat revenue are significant.
Blended ROAS calculator FAQ for multichannel reporting
Can channels use different attribution windows?
They can, but the blended result becomes harder to interpret. Align attribution windows and revenue definitions where possible, or disclose the differences beside the report.
Should agency fees be included in spend?
Include them when the goal is total marketing efficiency. Exclude them only when comparing platform media delivery, and label the scope clearly.