Short answer: ROAS measures revenue, ROI measures profit. ROAS divides the revenue generated by the advertising spend (ROAS = revenue ÷ ad spend). ROI subtracts every cost before dividing (ROI = (profit − investment) ÷ investment). That is why ROAS is always a positive multiple and ROI can be negative on exactly the same data.
The difference is not semantic. A ROAS of 4 in a business with a 25% gross margin is a negative ROI: you are selling more and losing money on every sale.
The two formulas
ROAS = attributed revenue ÷ advertising spend
It is a media efficiency ratio. It knows nothing about your cost of goods, your logistics or your payroll. It is expressed as a multiple (4) or as a percentage (400%).
ROI = (net profit − investment) ÷ investment
It is a profitability ratio. It includes cost of goods, shipping, payment fees, returns, tools, agency fees and any other associated cost. It is expressed as a percentage and it can be negative.
The same case, worked out both ways
A one-month campaign in an ecommerce business:
- Advertising spend: €10,000
- Attributed revenue: €40,000
- Cost of goods sold (60% of retail price): €24,000
- Shipping and payment gateway: €3,200
- Returns (8% of orders, net cost): €2,100
ROAS = 40,000 ÷ 10,000 = 4. Sounds like a winning campaign.
ROI: profit before advertising is 40,000 − 24,000 − 3,200 − 2,100 = €10,700. Subtract the €10,000 of advertising and €700 of profit is left. ROI = 700 ÷ 10,000 = 7%.
A ROAS of 4 that is really a 7% return. Drop the margin two points or push the return rate to 12% and that same ROAS of 4 becomes a negative ROI, with the platform dashboard showing exactly the same number in green.
When to use each one
It isn't that one is better: they operate at different layers.
- ROAS: to decide inside the account. Comparing campaigns, ad sets, creatives and audiences against each other. They all share the same cost structure, so ROAS ranks them correctly, and it is also the only one of the two the platform can optimise against in real time.
- ROI: to decide whether the channel exists at all. Whether you keep investing, whether the channel takes more budget and whether the business makes money. It is the board-level metric, not the metric for the person adjusting bids on a Tuesday.
The practical bridge between the two is the break-even ROAS: the exact ROAS above which your ROI stops being negative. Once that number is calculated, you can keep working with ROAS day to day knowing where the waterline is.
The three places where the comparison breaks
- ROAS depends on attribution and ROI doesn't. Changing the attribution window from 7-day click to 1-day click can knock 30% off reported ROAS without moving ROI by a cent. If you compare the two numbers across periods with different settings, you are not comparing anything.
- ROI needs a long period. Costs like returns or failed payments arrive weeks late. An ROI calculated over the last 7 days is optimistic by construction.
- Neither of them sees customer lifetime value. In repeat-purchase or subscription businesses, both undervalue the campaign if they only look at the first order. There the right metric is the relationship between LTV and CAC.
The rule we apply
In the accounts we manage, the target ROAS is never agreed in a meeting: it is calculated from margin and revisited when margin changes. The sequence is: real margin → break-even ROAS → target ROAS with the contribution the business wants → that number goes into the platform's bidding. That way the team can work with ROAS all month, which is the operational metric, without losing sight of ROI, which is what pays the salaries.
It is also why we report to clients on business numbers rather than dashboard numbers. Across our history that adds up to €18M of media managed and €220M billed by our clients — more than €10 back for every euro invested, aggregated, never a promise for a specific account. Read the detail in our case studies.
Frequently asked questions
Is a ROAS of 4 the same as a 300% ROI?
No. That conversion would only hold if your product cost nothing. A ROAS of 4 means €4 of revenue for every euro invested; to get to ROI you first have to subtract cost of goods, shipping, fees and returns. With typical ecommerce margins, a ROAS of 4 usually lands on a single-digit ROI.
What is the difference between ROI and ROAS in one sentence?
ROAS measures how much revenue advertising generates; ROI measures how much profit is left after paying every cost, advertising included.
Can ROAS be negative?
No. ROAS is a ratio between two positive quantities: the floor is zero (no sales at all). ROI can be negative, and it is whenever the profit generated does not cover the investment.
Which metric does an investor or a CFO ask for?
ROI or, in its aggregate marketing version, MER checked against margin. Platform ROAS is an account-management metric: outside the paid media team it says very little, because it carries no cost structure and no channel overlap.
How do I calculate my break-even ROAS?
Divide 1 by your gross margin as a decimal. With a 35% gross margin, break-even ROAS is 1 ÷ 0.35 = 2.86: below that number every extra sale loses money. Add the contribution the business needs on top of that to get your target ROAS, and recalculate it whenever cost of goods, shipping or return rates move.
Does your target ROAS come from your margin or from a meeting?
The Viability Diagnostic calculates your real break-even point and compares it with where you stand today. 5 minutes, no strings attached.