How to Calculate ROAS (and Why Your Dashboard Overstates It)

Almost everyone running ads knows the acronym ROAS. A surprising number read it wrong — and set budgets on that reading. This post covers how to calculate ROAS, where the formula stops being useful, and why the figure in your ad account rarely matches the one in your books.

What ROAS actually measures

ROAS stands for return on ad spend. It tells you how much revenue each unit of ad budget brings back.

ROAS = revenue from ads ÷ ad spend

Spend £1,000, generate £4,000 in sales, and your ROAS is 4 — or 400%. Every pound returned four. That part is easy. Interpretation is where it goes wrong.

ROAS is revenue, not profit

This is the point most often missed. ROAS measures revenue. It says nothing about profit. A ROAS of 4 sounds excellent, but once cost of goods, shipping, returns and overheads are accounted for, the same number can describe a loss.

Work it through:

Line	Amount
Revenue	£4,000
Cost of goods (40%)	−£1,600
Shipping and packaging	−£320
Returns (8%)	−£320
Payment fees (2%)	−£80
Ad spend	−£1,000
Left	£680

£680 before rent, software and salaries. If fixed costs exceed that, the month lost money at a ROAS of 4.

Your break-even ROAS

Every business has a break-even ROAS — the point where advertising starts paying for itself.

Break-even ROAS = 1 ÷ contribution margin

If your margin after cost of goods and variable costs is 30%, break-even is 3.33. Anything below that burns cash. At a 60% margin, break-even drops to 1.67 and a ROAS of 2 is already profitable.

Without this number, no ROAS is “good” or “bad”. It is just a number.

Why the platform number is inflated

The second big trap. The figure Meta or Google reports follows that platform’s own attribution rules, and those rules are generous to the platform:

• Attribution windows. Meta counts clicks within seven days and views within one by default. A purchase that would have happened anyway gets credited to the ad.
• Every platform counts separately. Someone sees a Meta ad, later clicks a Google ad, and both dashboards claim the sale. Add them up and you get more revenue than you actually made.
• Modelled conversions. What tracking loses gets estimated and extrapolated.

The honest cross-check is unglamorous: blended ROAS = total store revenue ÷ total ad spend across all channels. That number can’t flatter itself, because it comes from your till rather than from an ad account.

When platform ROAS and blended ROAS drift far apart, tracking is usually the cause. A properly configured Meta Pixel and Conversions API setup closes part of that gap.

What to steer by instead

1. Contribution per order, not revenue. It shows what actually remains.
2. Blended ROAS as the headline metric; platform ROAS only for steering individual campaigns.
3. Repeat rate. A ROAS of 1.8 can be profitable if customers order three times a year.
4. Trend, not snapshot. Daily figures swing. A weekly average is the smallest unit worth a decision.

What counts as a good ROAS?

Any honest benchmark depends entirely on the business model. Roughly:

• Thin-margin e-commerce: you need 3–5 to make money
• High-margin or subscription brands: 1.5–2.5 can be enough
• Services and consulting: ROAS barely applies — cost per qualified enquiry and close rate matter more

Anyone who gives you a target ROAS without knowing your margin is guessing.

The short version

The formula takes ten seconds. It becomes useful only once you know your break-even, check the platform figure against your own books, and steer by contribution rather than revenue.

If you’d like to go through your numbers together, get in touch — on the first call we work out your break-even ROAS before you commit more budget.