The minimum return on ad spend at which an order neither makes nor loses contribution margin, equal to 1 divided by your contribution margin percentage.
Break-even ROAS is the ROAS threshold below which an order destroys margin and above which it builds it. In its simplest per-order form it is 1 divided by your margin percentage. The textbook and competitor versions compute this on gross margin: Skup puts break-even ROAS as 1 divided by gross profit margin, the minimum ROAS at which an order neither makes nor loses money before ad cost (skup.net). Blufire instead computes it on contribution margin, the lower figure that also nets out fulfilment, payment fees, shipping, and returns. Because contribution margin is always at or below gross margin, 1 / CM% is at or above 1 / GM%, so the contribution-margin break-even is a higher, more honest threshold: it tells you the ROAS an order must clear to be profitable after everything variable, not just after COGS.
There is a separate customer-level form that is sometimes also called break-even, and it is not the same quantity as 1 / margin. Triple Whale computes it by multiplying AOV by gross margin and subtracting CAC; when the result is zero the first order breaks even, which solves to AOV divided by CAC (triplewhale.com). That construction folds the acquisition cost into the threshold for a single first order, so it answers a customer-first-order question, whereas 1 / CM% answers a per-order margin question. Keep the two distinct: the per-order break-even is 1 / CM%; the AOV-x-margin-minus-CAC=0 form is the Triple Whale customer-first-order break-even.
Worked example (Demonstrative): a SKU with a 40% contribution margin has a per-order break-even ROAS of 1 / 0.40 = 2.5x. The same SKU at a 50% gross margin would show a flattering 1 / 0.50 = 2.0x break-even, but that ignores fulfilment, fees, shipping, and returns. Any attributed revenue per ad dollar below the true 2.5x is losing contribution margin on that SKU, even if a platform dashboard calls the campaign 'profitable' at a 1.5x ROAS.
The Blufire difference is that break-even ROAS is derived from your real CM% per SKU and per channel, not a flat gross-margin assumption. A 30%-CM hero product and a 60%-CM accessory have different break-even thresholds, so a single account-wide target hides which lines are actually paying their way.