ROAS Calculator

The calculation itself

Return on ad spend is revenue attributed to advertising divided by the advertising spend: ROAS = revenue ÷ spend. A 3.0 ROAS means three dollars of revenue for every dollar spent.

It is a revenue ratio, not a profit ratio, and that distinction is the source of most of the trouble it causes. Whether a given ROAS is profitable depends entirely on the contribution margin behind the revenue.

The profitable threshold is 1 ÷ contribution margin, which on a 55% margin is 1.82 and on a 30% margin is 3.33.

In practice

$4,000 of spend producing $12,000 of attributed revenue is a 3.0 ROAS.

At a 55% contribution margin that revenue carries $6,600 of contribution, so after the $4,000 of spend the campaign generated $2,600 of profit.

Now the same 3.0 ROAS on a 30% margin product: $3,600 of contribution against $4,000 of spend, a $400 loss, on identical campaign performance.

The number on the dashboard is the same in both cases. Only the margin behind it says which one is a business and which is a leak.

Where the figure deceives

Attribution decides the numerator. A platform crediting itself with any conversion within a seven-day click and one-day view window will report a ROAS well above what an independent measurement shows, and the gap varies by platform and by how much brand demand already exists.

It also ignores incrementality entirely. Revenue from customers who would have bought anyway counts in full, which is why branded search campaigns report spectacular ROAS while adding very little.

Acting on it

Calculate your break-even ROAS from contribution margin before setting any target, and set the target at 1.3 to 1.5 times it so there is room for fixed costs and profit.

Then compare the platform-reported figure against blended ROAS, total revenue divided by total ad spend, over a month. The gap between them is a direct measure of how much attribution is over-claiming.

Why ROAS targets borrowed from other businesses are useless

A ROAS target is a restatement of a margin, and margins differ enormously between businesses. A 2.0 target is generous for a software business at 90% margin and impossible for a retailer at 25%.

Advice specifying a ROAS number without specifying the margin behind it is therefore advice about someone else's business. The only correct starting point is your own contribution margin.

The second correction is that a single account-wide target is usually wrong too, because different products have different margins. A target set for the catalogue average will overspend on the thin-margin products and underspend on the fat ones, and segmenting campaigns by margin band is the straightforward fix that almost nobody applies.

Separately, new-customer ROAS against returning-customer ROAS. Advertising that reaches existing customers reports excellent returns and adds very little, because those people were already going to buy.

Most platforms allow the two to be separated, and the new-customer figure is the one that measures acquisition. Accounts optimising on blended ROAS reliably drift toward retargeting existing buyers, which improves the reported number while shrinking the business.

The same split applies to prospecting and retargeting, which should never share a target for the same reason.