When marginal ROAS falls as you scale
Find out whether the next budget increase can earn its way back.
Calculate the change, not the blend
A campaign moves from $3,000 in spend and $15,000 in net revenue to $4,000 and $18,000. Blended ROAS is 4.5×, but the extra $3,000 in reported revenue divided by $1,000 in extra spend gives a marginal estimate of 3×.
Set a threshold for the next tranche
At a 30% contribution margin, break-even is 3.33×. The additional revenue leaves $900 before ads, so the additional $1,000 in spend appears to lose $100. Keep the existing budget and evaluate the proposed increase as separate decisions.
Check for changes unrelated to spend
The two periods may differ in seasonality, promotions, or conversion maturity. Where practical, compare an increased-budget group with a group that holds spend steady. Inspect marginal contribution after returns and document how long the test can run before reaching the loss limit.
Try a related tool
Compare revenue per advertising dollar with the return needed to cover ad spend. Enter net revenue and contribution margin before ads.
