The short answer
To combine ROAS across non-overlapping campaigns, add their attributed revenue and divide by their combined ad spend. Do not average the displayed ratios unless each observation has equal spend. The correct weighting for ROAS is advertising spend.
Combine two campaign results
Use one currency and non-overlapping revenue. Totals from platforms claiming the same order are not additive. Inputs stay in your browser. Displayed results are rounded.
Calculate from the raw amounts
Illustrative inputs: campaign A spends $200 and records $1,000 revenue; campaign B spends $800 and records $1,600. Their individual ROAS values are $1,000 ÷ $200 = 5× and $1,600 ÷ $800 = 2×. Combined ROAS is ($1,000 + $1,600) ÷ ($200 + $800) = 2.6×. The simple average, (5 + 2) ÷ 2 = 3.5×, overstates the aggregate result.
Equivalent weighted ROAS = sum of (campaign ROAS × campaign share of spend)
Cross-check the weights
In the example, A’s spend share is $200 ÷ $1,000 = 0.20 and B’s is $800 ÷ $1,000 = 0.80. The weighted result is 5 × 0.20 + 2 × 0.80 = 2.6×. The weights sum to one. Calculating from original totals avoids errors from rounding the individual ratios first.
Apply the same rule to daily reports
A day with very little spend should not influence the period’s ratio as much as a high-spend day. Sum revenue and spend over the required dates. Retain days with spend but no revenue. Excluding them because the return looks poor biases the result. If the total spend is zero, the aggregate ratio is undefined.
Check whether revenue is additive
The arithmetic assumes the revenue amounts can legitimately be added. Two platforms may both claim the same order, so adding their attributed revenue does not necessarily produce unique business revenue. Use deduplicated store totals for a blended view, or keep platform views separate with their attribution rules disclosed.
Keep margin outside the weighting shortcut
A correct combined ROAS still does not resolve different product margins. Pair it with total contribution after advertising. If you only have individual ratios and no spend weights, you do not have enough information to reconstruct the aggregate precisely. Ask for the underlying totals rather than supplying an unweighted approximation without a label.
Combine the raw totals
- Gather: Collect revenue and spend for non-overlapping campaigns or periods.
- Produce: Sum the amounts first; use spend shares only as a cross-check.
Decision boundary: Campaign ratios alone cannot reconstruct a weighted total without their spend weights.
Next reading
Examples are illustrative, not client results or benchmarks. The calculations use the inputs shown; real-world decisions depend on your records and assumptions. Report a correction.