ROAS is often treated as the ultimate measure of paid media success. Agencies report it. Businesses celebrate it. Dashboards are built around it. But on its own, it's a dangerously incomplete metric — and relying on it without context can lead you to scale campaigns that are generating revenue while quietly destroying profit.
It ignores cost of goods, service delivery, staffing, overheads, refunds, discounts, and churn. When these costs aren't accounted for, businesses end up scaling campaigns that look brilliant on paper and perform terribly on the P&L.
What ROAS Actually Measures
ROAS — Return on Ad Spend — is simply revenue from ads divided by ad spend. If you spend £10,000 on ads and generate £50,000 in revenue, your ROAS is 5x. That looks great. But it tells you nothing about whether the business made any money.
The problem is that revenue and profit are very different things in most ecommerce businesses. And in businesses with slim margins, high overheads, or high return rates, a 5x ROAS can mean a loss.
A Real Example — The Numbers That Matter
Let's walk through a straightforward DTC example to show exactly how this works.
The campaign generates £5,000 in revenue — a 5x ROAS. The agency sends a glowing report. But let's look at what actually happened.
| Revenue from ads | £5,000 |
| Cost of goods (35% of £5,000) | − £1,750 |
| Gross profit | £3,250 |
| Gross profit | £3,250 |
| Ad spend | − £1,000 |
| Profit after ad spend | £2,250 |
| Revenue from ads | £5,000 |
| Units sold (£5,000 ÷ £100) | 50 units |
| Net profit per unit after all overheads | £10 |
| Total net profit (50 × £10) | £500 |
| Ad spend | − £1,000 |
| Real profit after ad spend | − £500 |
A 5x ROAS sounds like a strong result. But when gross margin is 65%, overheads reduce net margin to 10%, and the ad spend is factored in — the campaign ran at a loss. ROAS told the business it was winning. The P&L told a different story.
What You Should Be Measuring Instead
ROAS has a role — it's a useful efficiency signal for comparing campaigns against each other. But it should never be the primary measure of whether paid media is working for the business. The metrics that actually matter are:
- Net profit per order — after cost of goods, fulfilment, overheads, discounts and refunds
- Break-even ROAS — the minimum ROAS needed to cover all costs and break even (1 ÷ net margin). At 10% net margin, your break-even ROAS is 10x, not 5x
- Customer Acquisition Cost (CAC) — what it actually costs to acquire a new paying customer, not just generate a click
- Customer Lifetime Value (CLV) — whether the acquired customer is worth the cost of acquisition over their lifetime
- MER (Marketing Efficiency Ratio) — total revenue divided by total marketing spend, giving a blended view across all channels
Only by including all of these can you see which campaigns are genuinely profitable — and which are generating impressive-looking ROAS numbers while quietly eroding the business.
The Break-Even ROAS Calculation
A simple and powerful starting point is calculating your break-even ROAS before you run any campaign. The formula is straightforward:
At a 25% net margin: Break-Even ROAS = 1 ÷ 0.25 = 4x
At a 40% net margin: Break-Even ROAS = 1 ÷ 0.40 = 2.5x
If your campaigns are running below your break-even ROAS, they are losing money — regardless of what the ROAS number looks like in isolation. This is the number your agency should be reporting against, not a standalone ROAS target set in isolation from your actual cost structure.