The short answer
Break-even ROAS is revenue divided by the contribution available before advertising. It tells you the revenue return needed to cover the costs in your model. Spending all of that contribution on ads leaves nothing for expenses you left out.
Build a complete order model
Start with the amount actually earned on an order after discounts. Choose a consistent treatment of shipping collected and tax. Subtract product costs, fulfillment, payment fees and other relevant variable expenses. Use paid amounts or documented assumptions, not a generic industry margin.
Maximum CPA at break-even = contribution before ads
Break-even ROAS = order revenue ÷ contribution before ads
Work through one order
| Component | Amount |
|---|---|
| Revenue after discount | $100 |
| Product cost | $40 |
| Shipping cost | $7 |
| Transaction fee | $3 |
| Other variable costs | $2 |
| Total non-ad costs | 40 + 7 + 3 + 2 = $52 |
| Contribution available for ads | 100 − 52 = $48 |
The break-even threshold is $100 ÷ $48 = 2.0833…×. Displayed to two decimals, that is 2.08×. Use the unrounded result for a precise comparison: exactly 2.08× is slightly below the unrounded threshold.
Read the margin shortcut correctly
If m is contribution before ads divided by revenue, break-even ROAS is 1 ÷ m. Use a fraction in this equation: 40% means 0.40. Product markup is not contribution margin.
| Assumed pre-ad contribution margin | Calculation | Break-even ROAS |
|---|---|---|
| 20% | 1 ÷ 0.20 | 5× |
| 30% | 1 ÷ 0.30 | 3.33…× |
| 40% | 1 ÷ 0.40 | 2.5× |
| 50% | 1 ÷ 0.50 | 2× |
Reserve contribution for overhead and profit
In the $100 example, suppose you want $15 left after ads. The ad allowance becomes $48 − $15 = $33. Required ROAS becomes $100 ÷ $33 ≈ 3.03×. That $15 is a planning choice, not a benchmark; it still has to cover any excluded fixed costs.
Know when the floor does not apply
- If costs equal or exceed revenue, there is no positive ad allowance under this order model.
- If the product mix changes, calculate total contribution across that mix rather than averaging individual thresholds.
- If the ad report excludes shipping revenue but the model includes it, align the numerators before comparing.
- If you rely on future repeat orders, show a separate cohort model instead of treating that revenue as already received.
Use the floor to identify whether the modeled offer can support acquisition. Use a higher cost-aware target and a measured performance comparison to decide what to spend.
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.