Every ad platform shows you a return on ad spend (ROAS) number. Very few of them tell you whether that number is good enough to keep the campaign running. The missing piece is your break-even ROAS: the lowest ROAS at which an ad campaign has paid for the product, the shipping and the fees, and has not yet made or lost you money. This guide explains the break-even ROAS formula, which margin to plug into it, how it connects to break-even cost per acquisition (CPA), and how to turn it into a practical target.
What ROAS means
ROAS is revenue generated per unit of advertising cost. Google's own help documentation describes a target ROAS as the average conversion value, "for example, revenue", that you would like to get for each dollar you spend on ads, and gives this example: $5 in sales divided by $1 in ad spend, multiplied by 100%, equals a 500% target ROAS. Some dashboards show ROAS as a percentage (500%) and others as a ratio (5.0, or "5x"). They describe the same thing, so check which one your platform uses before comparing numbers.
The formula is simple:
ROAS = conversion value (revenue) from ads ÷ ad cost
ROAS only measures revenue against ad cost. It says nothing about what it cost you to make, pack and ship the product. That is why a campaign showing 3x can be profitable for one store and a money-loser for another.
The break-even ROAS formula
Break-even ROAS is the ROAS at which the profit left after all non-ad costs exactly equals your ad cost. Using plain algebra:
Break-even ROAS = 1 ÷ contribution margin
where contribution margin is expressed as a decimal (40% = 0.40). Here is why it works. If each $1 of revenue leaves you a margin of m after product, shipping, fees and other variable costs (but before ads), then $1 of ad cost is covered when revenue × m = ad cost. Rearranged, revenue ÷ ad cost = 1 ÷ m.
An illustrative example (these numbers are invented for the sake of the maths, not data from a real store):
- Average order value: $80
- Product cost, shipping, payment fees and packaging for that order: $48
- Contribution margin before ads: ($80 − $48) ÷ $80 = 0.40, or 40%
- Break-even ROAS: 1 ÷ 0.40 = 2.5
At a ROAS of 2.5, a campaign spending $100 returns $250 in revenue; after $150 of variable costs (60% of revenue) and the $100 of ad spend, the order-level result is zero. Anything below 2.5 loses money on a contribution basis, and anything above it makes money.
Which margin should you use?
This is a common place for break-even ROAS calculations to go wrong. There are three common choices, and they give three different answers.
- Gross margin (revenue minus cost of goods). This is the easiest to find but usually overstates your real margin, because it ignores shipping, payment processing, packaging and returns.
- Contribution margin (revenue minus all variable costs except advertising). This is the right margin for break-even ROAS, because it captures every cost that scales with an order.
- Net margin (after fixed costs and everything else). Net margin already has advertising baked in, so using it double counts your ad spend.
To build a contribution margin that you can trust, subtract at least these items from the average order value:
- Cost of goods sold (what you paid for the product)
- Outbound shipping and packaging that you pay, not the customer
- Payment processing fees and platform transaction fees
- Expected refunds, returns and chargebacks (as an average share of orders)
- Discounts and promotional codes used on ad-driven orders
- Sales tax or VAT, if it is included in your revenue figure (tax you collect and remit is not your revenue, so the cleaner fix is to remove it from revenue)
If a platform reports revenue that includes tax or shipping charged to the customer, strip those out or make sure your cost side matches. Mismatched definitions can make break-even figures look better than reality.
Break-even CPA: the same idea per order
Some teams prefer to manage on cost per acquisition (CPA), the ad cost to get one order, instead of ROAS. The two are two views of the same constraint.
Break-even CPA = average order value × contribution margin
Using the illustrative store above: $80 × 0.40 = $32. If you spend more than $32 in ads to get one order, you lose money on that order's first purchase. Check: break-even ROAS = AOV ÷ break-even CPA = $80 ÷ $32 = 2.5, the same answer as before.
CPA is easier to explain to a team ("we can pay up to $32 for a customer") and ROAS is easier to compare across campaigns with different order values. Use whichever is clearer, but keep both consistent with the same contribution margin.
From break-even to target ROAS
Break-even is a floor, not a goal. Running a campaign exactly at break-even leaves nothing to cover overhead such as salaries, software and rent, and no cushion for the normal swings in conversion rates. A practical way to set a target is to decide what profit you want from each dollar of revenue, then deduct it from the margin:
Target ROAS = 1 ÷ (contribution margin − desired profit after ads)
If the illustrative store wants 10% of revenue left after ads: 1 ÷ (0.40 − 0.10) = 3.33. So the campaign needs a ROAS of about 3.3 to meet that goal.
Two cautions when setting targets:
- A target is only as accurate as the margin behind it. If your product mix is uneven, a single store-wide margin can hide the fact that some products are far less profitable than others. Where possible, calculate break-even ROAS by product group or by campaign.
- Do not set a target you cannot measure. If your ad platform and your store analytics disagree on attributed revenue, use the number you trust for decisions and apply it consistently.
First-order versus lifetime value
Break-even ROAS on the first order is the strict version. Many stores accept a lower first-order ROAS because customers come back and buy again. If you plan to do this, do it deliberately. Estimate the repeat-purchase value from your own order history, not from an industry guess, and decide how long you are willing to wait to recover the ad cost. A store with thin cash reserves may prefer the strict first-order floor, since waiting for repeat orders ties up money in advertising.
How to use the number day to day
- Label every campaign with its break-even ROAS in your reporting sheet, so that a result of "2.1" is immediately readable as above or below the line.
- Recalculate when your costs change. A supplier price rise, a shipping rate change or a new discount policy all shift your margin and therefore your break-even point.
- Watch the lag. Orders and returns settle after the ad click, so recent campaign numbers can look better than they will end up once refunds arrive.
- Separate new and returning customers if your tools allow it, because ads can receive credit for customers who would have bought anyway.
- Review by product, not just by account. A high-margin product can support a lower ROAS than a low-margin one in the same campaign.
Common mistakes
- Using gross margin and ignoring shipping, fees and returns.
- Mixing a percentage ROAS (250%) with a ratio break-even (2.5) when comparing.
- Treating the platform's reported ROAS as final without checking it against actual store revenue.
- Setting the target equal to break-even and leaving no room for overhead.
- Applying one margin to products that have very different costs.
Summary
Break-even ROAS equals one divided by your contribution margin, and break-even CPA equals your average order value multiplied by that same margin. Get the margin right by including every cost that scales with an order except advertising, label each campaign with its break-even line, and set a target above that line so the business keeps something after ads. The calculation takes minutes, and it turns a platform's ROAS figure from a vanity number into a decision rule.
This article is general information about advertising arithmetic, not financial or tax advice. Your own margins, costs and attribution settings will differ.
Sources
- Google Ads Help, target ROAS article (definition of target ROAS and the $5 ÷ $1 × 100% = 500% example): https://support.google.com/google-ads/answer/6268637
- The break-even formulas (1 ÷ margin, AOV × margin) and the target-ROAS adjustment are derived algebraically in this article from the ROAS definition above; the dollar figures in the examples are invented illustrations, not statistics.
