Is your 4x ROAS hiding negative profit?

Break-even ROAS equals 1 divided by your gross profit margin percentage — if your gross margin is 30%, break-even ROAS is 1/0.30 = 3.33x. At a 3.33x ROAS, every £1 of ad spend generates £3.33 of revenue, of which £1 is product cost and £1 is ad spend, leaving £1.33 of gross profit that offsets the £1 advertising investment and returns nothing further. For true profitability you need to exceed break-even by enough to cover fixed overhead. The Margin Erosion Audit calculates break-even ROAS per product category using your Merchant Center COGS data because margins vary by product type and an account-level average hides which categories are genuinely profitable.

2x — because break-even ROAS = 1 / gross margin, and 1/0.50 = 2.0. At a 2x ROAS, every £1 of ad spend generates £2 of revenue, £1 of which is COGS and £1 is ad spend, netting zero before overhead. If you see a 2x ROAS celebrated on a 50% margin product, recognise that you are literally breaking even on unit economics and making zero contribution to fixed costs. For meaningful profit, target 2.5–3x on 50% margin products. The Margin Erosion Audit calculates the exact break-even ROAS per product category so you know which products are profit-positive at their current performance.

Four common reasons: (1) you're measuring gross revenue but not subtracting returns, refunds, and chargebacks (which can run 15–30% in apparel, higher in some categories); (2) your COGS includes variable costs (shipping, payment processing, fulfilment) that eat further into margin; (3) your ROAS is blended across product categories and the winners are subsidising losers; (4) your reported ROAS includes view-through and modeled conversions that don't reflect causal revenue. A 4x reported ROAS can easily be a true 1.8x after adjusting for all four. The Margin Erosion Audit produces a revenue-to-profit waterfall that strips out each layer so you see your True Profit After Ads.

Start with reported conversion value, then subtract in this order: (1) return and refund rate applied to revenue (typically 10–30% in ecommerce), (2) COGS (product cost), (3) variable fulfilment costs (shipping, payment processing, platform fees at 2.5–5%), (4) ad spend itself. What remains is True Profit After Ads — the actual money left from the revenue that advertising generated. For most accounts, True Profit After Ads is 30–50% of what reported ROAS implies. The Margin Erosion Audit produces this waterfall per campaign so you see which campaigns generate real profit versus which generate revenue at a loss.

Profit (POAS — Profit on Ad Spend), not revenue ROAS — because Smart Bidding given only revenue optimises toward low-margin high-velocity products, systematically starving your high-margin SKUs. The implementation: pass margin-adjusted conversion values to Google Ads via dynamic value rules or by sending profit rather than revenue as the conversion value via the Google Ads API. Some accounts use a 'profit multiplier' per product group instead of true POAS — simpler but less precise. The Margin Erosion Audit checks whether your account passes margin-aware conversion values and recommends the specific implementation path based on your tech stack.

The formula is: Target ROAS = (1 + desired profit margin) / gross profit margin. For a product with 40% gross margin and a 10% desired profit contribution after ads, target ROAS = 1.10 / 0.40 = 2.75x. This ensures you clear COGS, ad spend, and a margin for overhead. Set this target per product category in separate campaigns — a single account-level target always under-serves high-margin products and over-bids on low-margin ones. The Margin Erosion Audit calculates category-specific target ROAS based on your actual margin data from Merchant Center.

Treat fulfilment costs as a margin reduction, not an overhead — if your gross margin is 40% but shipping costs you 8% of revenue and payment processing 3%, your true contribution margin is 29%. Your break-even ROAS then becomes 1/0.29 = 3.45x, not the 2.5x implied by gross margin. Many accounts set targets at the gross margin break-even and wonder why they're unprofitable despite 'hitting' ROAS. The Margin Erosion Audit subtracts fulfilment and processing from reported revenue in its ROAS calculation so the target ROAS you set reflects actual unit economics.

Split your catalogue into margin tiers using custom labels in the Merchant Center feed (e.g., custom_label_0 = 'margin_high' for 50%+ margin SKUs, 'margin_mid' for 30–50%, 'margin_low' for under 30%), then run each tier in a dedicated Shopping campaign with its own Target ROAS. High-margin tier can carry a 2x target and remain highly profitable; low-margin tier needs 4–5x minimum. This is the only way to prevent Smart Bidding from disproportionately funding low-margin winners. The Margin Erosion Audit produces the exact tier assignment for every SKU and the recommended Target ROAS per tier.

A common pattern: a campaign reports 5x ROAS which looks excellent, but the product category has a 15% gross margin (break-even ROAS 6.7x), a 20% return rate, and 5% payment processing. After adjustments, True ROAS is roughly 3.4x — well below break-even. The campaign is destroying margin at scale, with every additional pound of ad spend increasing losses. This is hidden by blended account reporting because other categories subsidise the losses. The Margin Erosion Audit produces a Kill List: products where current ROAS cannot recover margin given actual category economics, with monthly loss per product quantified.

Work out your contribution margin (gross margin minus variable fulfilment, payment processing, returns reserve), then divide 1 by that percentage. For a product with 40% gross margin, 8% fulfilment, 3% payment processing, and a 10% return reserve, contribution margin is 40 - 8 - 3 - 4 = 25%, and break-even ROAS is 1/0.25 = 4x. Many accounts calculate break-even at gross margin only (2.5x for 40% gross) and miss the variable cost layer entirely. This is why 'profitable ROAS' accounts can still be cash-negative. The Margin Erosion Audit calculates contribution margin from your feed data including all four layers.

Products meeting any of three criteria: break-even ROAS above 6x (very thin margins demanding unrealistic ad efficiency), actual ROAS below break-even for 60+ days despite optimisation attempts, or average order value too low to generate enough gross margin to cover competitive CPCs in the category. Specifically, a £20 product at 30% margin yields £6 of gross profit per sale — if the category CPC averages £0.80 and conversion rate is 2%, your CPA is £40, meaning you lose £34 on every sale. The Margin Erosion Audit's Kill List identifies these products and quantifies the monthly loss each is generating so you can prioritise which to exclude first.