Insight

RoAS Is Not
Profit

A 4.0 RoAS can lose money. A 1.8 RoAS can scale. The difference is unit economics.

Return on ad spend is a ratio: revenue the ads claim, divided by what you paid for them.

It knows nothing about your margin, nothing about what a customer is worth, nothing about how long you wait to get your money back.

Founders who understand that scale. The ones who don't hit a ceiling, and wonder why more media optimisation never moves it.

01 — The Trap

A "good" RoAS that loses money

A brand sells a £120 product. Meta reports a RoAS of 4.0. The dashboard is green, the media buyer is pleased and the founder thinks he is scaling.

Gross margin is 45%. After cost of goods, transaction fees and shipping, £38 of that £120 stays in the business. The product is a one-and-done — nobody buys a second. There is no retention curve to rescue it.

They paid £30 to win the customer and kept £38. That is £8, before the team, the warehouse, the tools and the rent. A 4.0 RoAS that barely breaks even.

They hit the target every month and still cannot grow, because the economics underneath will not carry it.

02 — The Reframe

You are not buying a transaction

First-purchase RoAS barely matters. You are not buying an order. You are buying a customer.

If that customer comes back, the second order costs nothing to acquire. Nor does the third. The arithmetic changes completely.

That is why one brand runs profitably at 1.8 while another bleeds at 4.0. The brand at 1.8 has a fat margin, real repeat purchase and a 60-day value that makes the first sale look like a deposit. It is not being reckless. It knows what a customer is worth.

03 — The Foundation

Four numbers before you set a target

Before you brief creative, restructure campaigns or move budget, you need these four.

01
Gross margin
Revenue minus cost of goods. Without a blended figure across the catalogue you have nothing to work back from, and everything downstream is a guess.
02
Contribution margin
Gross profit minus shipping, fees, processing, discounts and returns. This is the real margin, and the ceiling on what you can pay for a customer.
03
Value at 30, 60 and 90 days
What a customer has actually spent by each of those marks. This tells you whether you bought an order or a relationship, and how long until it pays.
04
Maximum CAC
The most you can pay for a customer and still make your margin. It falls out of the three numbers above, and it sets your RoAS target.

// Your RoAS target is an output of these four numbers. Set it first and you are optimising a figure with no connection to your bank balance.

04 — The Proof

Three brands. Three targets. All profitable.

The number means nothing without the economics behind it.

Brand A
0.6x
Scaling profitably
Subscription wellness. 82% gross margin, and by day 90 a customer has spent 4.2 times the first order. They lose money on day one and get it back by day 60. A 0.6 would frighten most founders. This one knows what it means.
Brand B
2.1x
Scaling profitably
Mid-range fashion. 58% gross margin, and two in five customers order again within 45 days. The target is set to that curve, and they know the week it pays back.
Brand C
6.0x
Scaling profitably
High-ticket home goods. Thin margin, almost no repeat purchase. They need 6.0 to break even on the first order, and they say so. The target is built from the economics, not from what sounds good on a call.

Three targets, ten times apart, all correct. Each came from the brand's own numbers rather than a benchmark report.

05 — The Pattern

The £10m-a-month brand isn't doing anything clever

The brands at the top have no secret account structure. They have three things:

  • A product people come back to without being bribed with a discount
  • A measured figure for what a customer is worth at 30, 60 and 90 days
  • A calculated ceiling on what they will pay to win one

The media buying, the creative testing, the campaign architecture: all of it matters, and all of it is downstream of those three.

06 — The Mistake

Should you pause at 1.8?

This is the costliest reflex in paid media. RoAS slips under some remembered threshold and the response is immediate: cut spend, pause campaigns, pull back.

But if you know your margin, your 60-day value and your maximum CAC, and the arithmetic still works at 1.8, you are not losing money. You are buying customers at a price the business can carry.

You cannot make that call on instinct. At scale, the gap between profitable and not is too narrow for a feeling.

07 — The System

This is what Fathom solves for

Working these numbers out by hand is miserable, so I built Fathom. It plugs into your Shopify store and your ad accounts and keeps the four numbers current.

Contribution margin
A monthly waterfall from revenue down through cost of goods, shipping, fees and ad spend. CM1 is your budget ceiling; CM2 is what you keep. Pulled from real orders, not a spreadsheet.
Value by cohort
What a customer is actually worth at 30, 60 and 90 days, split by the channel that brought them in, so you can see which sources send people who stay.
CAC payback
Cost per customer by channel, with the curve that shows how many days it takes each one to turn profitable. The answer differs by channel, often sharply.
Target RoAS
The breakeven figure, built from your margin, your variable costs and your measured repeat rate. The minimum you need, derived rather than borrowed.

The premise is simple: a brand that knows its numbers can scale on paid ads.

08 — The Takeaway

Know the numbers before you touch the campaigns

RoAS earns its keep as a signal for the algorithms. Pick the wrong one and you have taught Meta to optimise towards something your bank account has never heard of.

Without your contribution margin you cannot know your breakeven RoAS. Without that, every spend decision is a guess.

RoAS is a front-end number. It should fall out of the back-end ones: margin, customer value, CAC.

Know Your Numbers

Fathom gives you the numbers. I help you act on them.

Back to The Playbook