A Google Ads account can report a 4.0 ROAS and still lose money. That is not a channel problem. It is a commercial maths problem. Before increasing spend, every serious retailer needs to calculate ecommerce breakeven ROAS from its actual contribution margin, not a rough gross-margin figure pulled from a spreadsheet six months ago.
Breakeven ROAS tells you the minimum revenue return required from advertising to cover the cost of the product, fulfilment and other variable costs, plus the ad spend itself. It is the line between buying profitable revenue and paying to grow turnover at a loss.
What ecommerce breakeven ROAS really means
ROAS is simply revenue divided by ad spend. If you generate £4,000 in tracked revenue from £1,000 in spend, your ROAS is 4.0.
Breakeven ROAS reverses that question: how much revenue must an advert generate for every £1 spent before the order stops making a contribution to profit? The answer depends on how much of each sale remains after all costs that move with that sale.
That remaining amount is contribution margin. It is not the same as gross margin. Gross margin usually removes only the cost of goods. Paid media decisions require a harsher view of the numbers.
For a direct-to-consumer retailer, contribution margin should normally account for product cost, transaction fees, picking and packing, shipping subsidies, packaging, expected returns or refunds, and any other cost that rises as order volume rises. If a cost is genuinely fixed in the short term, such as rent or a salaried team member, it does not usually belong in the first calculation. But it still matters when deciding what a sustainable profit target looks like.
The formula to calculate ecommerce breakeven ROAS
Start with your contribution margin percentage before advertising:
Contribution margin % = (Revenue – variable costs excluding ad spend) / Revenue
Then calculate breakeven ROAS:
Breakeven ROAS = 1 / contribution margin %
Use the percentage as a decimal. A 40% contribution margin becomes 0.40, not 40.
A worked example
Assume an average order value of £100, excluding VAT where appropriate. The costs attached to that order are £35 for stock, £5 for fulfilment and packaging, £2.50 for payment processing, £7.50 in delivery subsidy and £5 allocated for returns.
That leaves £45 before advertising. Your contribution margin is therefore 45%.
The breakeven calculation is:
1 / 0.45 = 2.22 ROAS
At a 2.22 ROAS, £1 of ad spend creates £2.22 in revenue. The £2.22 sale leaves £1 of contribution after variable costs, which covers the £1 spent acquiring it. You have broken even before fixed overheads and tax.
Anything below 2.22 is loss-making on that first-order basis. Anything above it produces contribution – but do not mistake that for a finished profitability target.
Why gross margin produces misleading ROAS targets
This is where otherwise competent brands make expensive decisions. A business with a 65% gross margin may assume it can afford a 1.54 breakeven ROAS. That calculation only works if stock is its sole variable cost.
It rarely is. Carrier costs rise. Payment fees apply to every transaction. Promotional codes reduce realised revenue. Returns can be material, especially in fashion, beauty and higher-consideration categories. International delivery and duties can change the economics again.
If those costs reduce the true contribution margin to 40%, the actual breakeven ROAS is 2.5, not 1.54. A campaign reporting 2.0 ROAS may look acceptable in a dashboard while quietly destroying cash.
The right approach is not to create one universal target for the whole business. Calculate it by product group, collection or margin band when the differences are meaningful. A high-margin accessory and a low-margin hero product should not be forced to operate to the same efficiency threshold merely because they sit in the same Shopping campaign.
Build the calculation from realised revenue
Use net realised revenue wherever possible. That means accounting for discounts, refunds and cancelled orders rather than relying solely on catalogue price or initial checkout value.
For VAT-registered UK businesses, calculations are generally cleaner when revenue and VAT-recoverable costs are shown excluding VAT. The key is consistency. Do not compare revenue excluding VAT with costs including it, or the result will overstate your available margin.
Returns deserve particular attention. You do not need to wait for every order to mature before making decisions, but you do need a sensible expected return rate based on recent cohort data. If a category returns 20% of revenue, pretending that it returns 5% because that is easier to report will make your paid-media targets fiction.
Subscription and repeat-purchase brands also need two views. First-order breakeven protects cash flow and tells you whether cold acquisition is viable without future purchases. Lifetime-value ROAS can justify acquiring a customer at a first-order loss, but only when retention data is proven, cash reserves support the payback period and repeat orders are genuinely incremental. Hope is not LTV.
Breakeven ROAS is not your target ROAS
Breakeven is a floor, not a growth plan. Operating a whole account at breakeven gives you no meaningful contribution towards payroll, software, warehousing, agency management or retained profit.
Set a target ROAS by deciding how much contribution you need to retain after advertising. Using the earlier example, a £100 order produced £45 of contribution before media. If the business wants to retain £15 per £100 of revenue after ads, it can spend a maximum of £30 to acquire that £100 revenue.
That means an allowable advertising cost of 30% of revenue, or a target ROAS of:
1 / 0.30 = 3.33 ROAS
The gap between 2.22 breakeven and 3.33 target is the margin needed to operate and grow properly. It may be narrower during an aggressive acquisition period or wider when cash preservation is the priority. The number should reflect the business objective, not an arbitrary industry benchmark.
Apply the number properly in Google and Meta
A single account-level ROAS target is useful as a guardrail, but it can be too blunt for day-to-day optimisation. Brand search often returns a higher ROAS than non-brand Shopping. Remarketing usually converts more efficiently than prospecting. Performance Max can blend several demand sources, while Meta may have a different role in creating demand before a branded search converts it.
Judge channels against their role, but remain accountable to blended profitability. Platform-reported ROAS is directional, not a finance report. Attribution windows, consent settings, cross-device journeys and delayed returns all affect what each platform claims.
Track at least three layers: platform ROAS for optimisation, channel-level profitability for budget decisions, and blended marketing efficiency against total store revenue for commercial control. If platform numbers improve while blended revenue and contribution do not, the account may be harvesting demand rather than creating profitable growth.
Product feeds matter here too. Accurate product costs and margin labels allow Shopping and Performance Max structures to prioritise the ranges that can carry spend. There is little value in scaling a best-selling item if its delivery, discounting and return profile mean it cannot meet the required ROAS.
Common errors that make profitable campaigns look better than they are
The most damaging mistake is using revenue rather than contribution as the basis for target setting. The second is forgetting costs that sit outside the ad platform, particularly returns and fulfilment.
Brands also often use average order value without checking whether paid traffic has a different basket mix from organic traffic. If paid customers buy lower-margin entry products, use more discount codes or return more often, the paid-media breakeven point is higher than the site-wide calculation.
Finally, do not change targets every few days because reported ROAS moves. Campaigns need enough conversion volume and a stable measurement period. React quickly to obvious waste, but make structural budget decisions using a meaningful data window and the actual cash economics behind it.
Profit-first PPC starts with a number the finance team recognises, then makes every bidding, feed and budget decision answer to it. Get the margin data right, set a target above breakeven, and scaling spend becomes a controlled commercial decision rather than a gamble.