ROAS stands for Return On Ad Spend and measures how much revenue each unit of money spent on advertising returns. It is calculated by dividing campaign revenue by ad cost: 10,000 KM of revenue against 2,500 KM spent gives a ROAS of 4, meaning 4 KM of revenue per unit invested.
The formula is simple: ROAS = revenue ÷ ad spend. It is expressed as a multiple, for example 4× or 3.2×, and sometimes as a percentage.
A ROAS of 1 means you recovered exactly what you put in - and that is a loss, because revenue is not profit. Cost of goods, wages and everything else still has to come out of it.
ROAS looks only at ad spend against revenue. ROI looks at total profit against total cost, including product, labour, tools and time.
That is why ROAS can look excellent while the business loses money. An online store with a 20 percent margin and a ROAS of 3 is actually losing: from 3 KM of revenue it earns 0.60 KM, having spent 1 KM on the ad.
A practical rule: the minimum ROAS you need equals 1 divided by your margin. At a 30 percent margin that is 3.3 - anything below means you are paying for the privilege of selling.
There is no universal number, and any pitch claiming otherwise is oversimplifying. In e-commerce with thin margins 4 and above is expected; in services with high deal value even a ROAS of 2 can be excellent.
The time frame matters too. A campaign bringing a customer who returns for years shows a weak ROAS in the first month and an outstanding one across the customer lifetime.
In services the cost per acquired enquiry is often measured instead of ROAS, because revenue does not arrive immediately but after a quote and negotiation.
If conversions are not set up properly, the numbers mean nothing. The most common error is counting the same enquiry several times, or treating a click on a phone number as a sale.
The second problem is attribution. A customer who saw an ad, returned through Google search and only then bought may be credited to the wrong channel - overvaluing one and undervaluing another.
That is why ROAS is read alongside total revenue rather than instead of it. If ROAS rises while overall sales fall, the measurement is lying.
The target return is not chosen by feel but derived from margin. If 100 KM of revenue leaves 30 KM of gross margin, the ad may spend at most 30 KM to break even - which means a minimum return of 3.3.
That figure is the survival threshold, not the goal. The goal sits above it, high enough to leave profit after fixed costs. In e-commerce with thin margins the gap between threshold and goal can be very small, so the room for error is narrow.
In services the maths runs differently. If one client is worth several thousand over a year of work, a campaign with an apparently weak return in the first month can be excellent. That is why services more often track cost per acquired enquiry than the return itself.
The budget is then set backwards: how many clients you want per month, how many enquiries one client takes, and what one enquiry costs. That calculation produces a realistic monthly figure rather than a number picked at random and justified afterwards.
Once a campaign works, the target is raised gradually. Tightening abruptly usually reduces both spend and sales, so total value falls even though the number on screen looks better.
Last updated: 17 August 2026
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