Ecommerce Break-Even ROAS Calculator: Use Contribution, Not Revenue

On an $80 order with 55% gross margin, $12 in other variable costs, and a 5% return allowance, maximum break-even CPA is $28 and break-even ROAS is 2.86× (285.7%).

This calculator starts with the money left before advertising, then asks how much of that contribution can be spent to acquire an order. The result is a planning guardrail for paid acquisition, not a forecast of future performance or a guarantee of profit.

Table of contents

• What break-even ROAS measures
• Formula and inputs
• Worked example
• Sensitivity and edge cases
• Decision workflow
• Guardrails-next-steps-and-limitations

What break-even ROAS measures

Break-even ROAS is a unit-economics threshold: the point where advertising cost consumes all contribution available from an order. It is more useful than a revenue-only target when the objective is to understand whether an order can pay for its own acquisition.

Revenue ROAS compares tracked conversion value with advertising cost. Google Ads describes target ROAS using conversion value relative to cost, while its campaign guidance explains revenue, cost, and ROI arithmetic. Google Ads target ROAS documentation and Google Ads campaign measurement guidance provide that platform context.

The calculator adds the costs that revenue ROAS does not reveal by itself:

A high revenue ROAS can still leave little or no contribution if margin is thin, other variable cost is high, or returns are material. The calculation therefore treats ROAS as a ratio built on top of contribution, not as a substitute for it.

Formula and inputs

Use four inputs to calculate contribution before ads, maximum break-even CPA, and break-even ROAS.

Contribution before ads = AOV × gross margin rate − other variable cost − AOV × return allowance rate

Maximum break-even CPA = contribution before ads

Break-even ROAS = AOV ÷ maximum break-even CPA

Percent ROAS = break-even ROAS × 100

Each input has one job:

• AOV: Average order value. In the supplied default, one order produces $80 in revenue.
• Gross margin rate: The share of AOV remaining after the gross-margin deduction. The default is 55%, so the gross-margin contribution is $80 × 55%.
• Other variable cost per order: The dollar cost that must be deducted from each order outside the gross-margin rate. The default is $12.
• Return allowance rate: The share of revenue reserved for returns or refunds. The default is 5% of AOV, or $4 on an $80 order.

Conversion values can be configured for advertising measurement, and Google Ads documents a profit-margin value option for assigning values that better reflect business economics. Google Ads conversion value guidance explains that value setup can account for profit-margin considerations. Separately, GA4 ecommerce documentation covers purchase and refund measurement, which matters when a return allowance is part of the planning model. GA4 ecommerce measurement guidance provides that measurement context.

The calculator’s maximum break-even CPA is not a recommended bid, a platform setting, or a promised acquisition cost. It is the highest modeled ad cost that leaves contribution after ads at zero.

Worked example

The supplied defaults produce $28 of contribution before ads, so $28 is the maximum break-even CPA.

At a 3.50× observed ROAS, modeled ad cost per order is $80 ÷ 3.50 = $22.86. Subtracting that cost from the $28 contribution before ads gives $28 − $22.86 = $5.14 of modeled contribution after ads per order.

That $5.14 is a calculation from the supplied inputs. It does not represent a SellerTrove-observed merchant result, and it does not account for costs or timing that are absent from the model.

Sensitivity and edge cases

Change one input at a time to see which assumption has the greatest effect on the guardrail. With the supplied $80 AOV, each one-percentage-point change in gross margin changes contribution by $0.80, and each one-percentage-point change in the return allowance changes it by $0.80 in the opposite direction.

Other variable cost changes contribution dollar for dollar. If that input rises by $3, maximum break-even CPA falls by $3. If it falls by $3, the modeled CPA ceiling rises by $3, assuming the other inputs stay unchanged.

AOV affects several parts of the formula. With rates held constant, a higher AOV increases both gross-margin dollars and the return allowance in dollars. The resulting contribution is AOV × (gross margin rate − return allowance rate) − other variable cost, and break-even ROAS remains AOV ÷ contribution before ads.

Product mix can make a single blended number misleading. If products have different margins, variable costs, or return allowances, calculate a weighted average only when the mix is stable enough for that assumption to be useful. Otherwise, run separate scenarios by product or category and compare their guardrails.

New and returning customers can also require separate scenarios. If their AOV, margin, return allowance, or other variable cost differs, one blended break-even ROAS can hide the economics of either group. Label the customer scope before comparing observed ROAS with the model.

Attribution delay is another reason to avoid treating an early ROAS reading as final. Purchases may be reported before all refunds are reflected in the planning view, so observed ROAS and contribution can change as the measurement window matures. Use the purchase and refund events in your measurement setup consistently; GA4’s ecommerce documentation describes those event types.

Two edge cases need an explicit decision:

• If contribution before ads is exactly zero, maximum break-even CPA is zero and break-even ROAS cannot support positive ad cost.
• If contribution before ads is negative, there is no positive break-even ROAS under this model. Review the inputs before treating paid acquisition as viable.

Decision workflow

Use the calculator as a repeatable decision workflow, not as a one-time target.

1. Set the scope. Decide whether the calculation covers all orders, a product group, a new-customer segment, or a returning-customer segment.
2. Define the inputs. Record AOV, gross margin rate, other variable cost per order, and return allowance rate using the same scope.
3. Calculate the guardrail. Compute contribution before ads, maximum break-even CPA, and break-even ROAS.
4. Compare observed ROAS. Use the same attribution scope and allow time for delayed purchases and refunds to be reflected.
5. Choose an action. If observed ROAS is below the guardrail, investigate the assumptions and acquisition economics before scaling. If it is above the guardrail, document why the positive modeled contribution is expected to persist.

A platform target can help direct bidding toward a conversion-value ratio, but this calculator answers a different question: how much revenue-to-ad-cost efficiency is required for the order to cover its modeled contribution economics. Keep those purposes separate. Google Ads target ROAS guidance describes the platform bidding concept.

Guardrails, next steps, and limitations

The table below translates the worked example into simple decision signals.

Once the guardrail table is documented, use SellerTrove’s ad-creative tools, pricing tools, and report to document the assumptions behind the comparison and decide what to review next.

This is a planning model, not a forecast, guarantee, or complete profit statement. It does not predict conversion volume, future AOV, future margin, customer mix, product mix, refund timing, or advertising cost. It also does not determine total business profitability after costs that are outside the four inputs.

The model is only as reliable as the definitions behind its inputs. Keep gross margin, other variable cost, and return allowance consistent across periods and segments. If uncertainty is high, calculate a range using conservative, base, and favorable assumptions instead of relying on one precise-looking ROAS threshold.

Finally, treat the result as a documented guardrail. Recalculate when prices, product mix, margin, return behavior, or measurement rules change. The goal is not to make revenue ROAS disappear; it is to connect that ratio to the contribution available to pay for acquisition.