Last year I walked into an e-commerce account where the founder had a weekly call with his old agency. „All good, 3.8× ROAS, best in six months." Eight months later he was 42,000 lei in the red. The ROAS had grown. The business had snapped. It's the kind of story you hear four or five times in your founder lifespan, and each time it feels new.
Let's get into the numbers. You'll see exactly where the logic breaks, and why ROAS on its own will never tell you whether you're making a good call.
Scenario. Two campaigns, same ROAS.
Online store with two categories. Electric scooters at 35% net margin. Accessories, helmets and chargers, at 8% net margin. Agency reports separately. 3× ROAS on both. On the report, identical.
| Scooter campaign | Accessories campaign | |
|---|---|---|
| Monthly budget | €5,000 | €5,000 |
| Revenue | €15,000 | €15,000 |
| ROAS | 3.0× | 3.0× |
| Net margin | 35% | 8% |
| Gross profit | €5,250 | €1,200 |
| POAS | 1.05× | 0.24× |
| Final profit | +€250 | −€3,800 |
The accessories campaign pulls €3,800 out of the company every month. But the report says „3× ROAS, good performance". If the agency scales accessories from €5,000 to €15,000 (and calls it „ROAS-based scaling"), the loss hits €11,400 a month. With weekly meetings full of nodding.
What changes once POAS is in the room
If POAS had been the decision metric, that meeting looked completely different.
- Scooters, 1.05 POAS. Clean break-even. You don't raise budget, you work on creative and CPM optimization to push POAS toward 1.4 before scaling anything.
- Accessories, 0.24 POAS. Obvious hemorrhage. Either kill the campaign, raise price 20% and test elasticity, or find a cheaper supplier. But you don't scale anything until one of those moves.
What decisions look like with POAS in front of you
With ROAS, decisions sound simple but dangerous. Scale what's big, cut what's small. With POAS, you get nuance that saves you from mistakes.
- 1POAS between 1.5 and 2.5, scale. Raise budget 20% a week and watch whether POAS holds.
- 2POAS between 1.0 and 1.5, hold. Iterate on creative and audiences, don't raise budget. Work on efficiency.
- 3POAS between 0.8 and 1.0, verify. If it brings high-LTV customers who repurchase, maybe keep it. Otherwise, cut.
- 4POAS below 0.8, pause the campaign and do a separate analysis. No discussion.
What to do when margin varies by product
In most stores, margin isn't a number. It's a spectrum. That's exactly why you have to calculate POAS at the campaign level, not across the whole account. Meta Ads Manager won't do it for you. GA4 won't either. It's manual work.
Practically, it's a Google Sheet. Columns: campaign, revenue, dominant product, product net margin, budget. One formula per row, POAS = (revenue × margin) ÷ budget. Twenty minutes a month. The only twenty minutes that actually matter.
When ROAS is genuinely useful
I'm not going to tell you ROAS is useless. It isn't. It has its role, and an important one.
- Quick benchmarking. 2× versus 4× ROAS gives you a rough sense of relative performance without digging into margin.
- Algorithmic optimization. Meta and Google optimize on purchase value, not on POAS. ROAS is the signal they read.
- Reporting to investors or partners who don't know the margin details. Here you label it clearly as „ROAS, not POAS", so you don't create confusion.
The trouble starts the moment ROAS becomes the only decision metric. That's when you start making choices that look good on PowerPoint and drain the bank account.
The Friday-evening test
Take the biggest campaign you're running right now. Four steps, ten minutes.
- 1Ask for net margin on the dominant product. No „estimate", no „around". Ask for an exact number, calculated with every variable cost.
- 2Pull last month's ROAS.
- 3Apply the formula. POAS = ROAS × net margin.
- 4If the result is above 1, you have room to scale. Between 0.8 and 1, optimize. Below 0.8, you have a serious issue and it needs to be addressed this week, not next month.