What does ROAS actually measure?
ROAS is revenue divided by ad spend. If you spend $1,000 and the platform reports $4,000 in sales, your ROAS is 4.0. It measures how much revenue ads are linked to, and nothing else.
It leaves out the cost of the product, shipping, payment fees, discounts and returns. It also depends on the platform's own attribution, which tends to give itself generous credit. That makes ROAS a useful signal for comparing ads inside one platform, and a poor guide to whether your business is making money.
What is contribution margin?
Contribution margin is what an order leaves you after its direct costs. It is the money that pays for rent, salaries and, eventually, profit.
For an online store, the usual direct costs are:
- Cost of goods sold, meaning what you paid for the product
- Shipping and fulfillment, including packaging and pick-and-pack fees
- Payment processing fees
- Discounts and coupons, if they are not already removed from revenue
- Returns and refunds
- Ad spend used to win the order
Subtract all of these from revenue and you have contribution margin after ads. That is the number worth growing.
A worked example: which campaign earned more?
The numbers below are hypothetical, chosen to show the math. Say you run two campaigns in the same month.
Campaign A promotes your best-selling product line. You spend $10,000 and the platform reports $40,000 in revenue, a ROAS of 4.0. These products have a 45% cost of goods.
Campaign B promotes a premium line with better margins. You spend $5,000 and get $15,000 in revenue, a ROAS of 3.0. These products have a 30% cost of goods.
| Hypothetical line item | Campaign A | Campaign B |
|---|---|---|
| Revenue | $40,000 | $15,000 |
| Cost of goods | −$18,000 | −$4,500 |
| Shipping and fulfillment | −$4,000 | −$1,500 |
| Payment fees (3%) | −$1,200 | −$450 |
| Returns (5%) | −$2,000 | −$750 |
| Contribution before ads | $14,800 | $7,800 |
| Ad spend | −$10,000 | −$5,000 |
| Contribution after ads | $4,800 | $2,800 |
| Contribution per ad dollar | $0.48 | $0.56 |
| ROAS | 4.0 | 3.0 |
Campaign A has the higher ROAS and the larger total. But each dollar spent on Campaign B returned 56 cents of contribution, against 48 cents for Campaign A. If Campaign B can scale without its costs rising, the next dollar likely belongs there, even though a ROAS-only report would say the opposite.
How do you find your break-even ROAS?
Break-even ROAS is one divided by your contribution margin rate before ads. Below it, every sale loses money. Above it, every sale adds some.
In the example, Campaign A keeps $14,800 from $40,000 in revenue before ads, a 37% rate. One divided by 0.37 is about 2.70, so Campaign A breaks even at a ROAS of roughly 2.7. Campaign B keeps $7,800 from $15,000, a 52% rate, so it breaks even at about 1.92.
That changes how you read targets. A ROAS of 2.5 loses money on Campaign A's products and earns money on Campaign B's. One account-wide ROAS target can't be right for both. You can run your own numbers in our ROAS calculator.
Why do platforms report more revenue than you made?
Each ad platform uses its own attribution rules and sees only its own touchpoints. When a shopper clicks a Google ad, sees a Meta ad and then buys, both platforms may claim the full sale.
Add up platform-reported revenue across channels and it often exceeds what your store actually took in. That is why we compare platform numbers against store orders, and why accurate purchase tracking matters. Our guide to server-side tracking explains how to make platform data line up more closely with real orders. For a fuller picture across channels, see marketing attribution.
What about new versus returning customers?
A sale to a returning customer who would have bought anyway adds little. A sale to a new customer can pay off for months through repeat orders.
So split ROAS and contribution by new and returning buyers when you can. Brand-name search campaigns often show very high ROAS because they catch people already on their way to you. Prospecting campaigns show lower ROAS but may bring in the customers who fuel next year's repeat revenue. Judge each by the job it is meant to do.
What should you change in your reporting?
Add three columns next to ROAS: contribution margin rate, break-even ROAS and contribution after ads. Review them by product line as well as by campaign.
- Export orders with product, cost of goods, shipping and fees for one month.
- Calculate contribution before ads for each product line.
- Find break-even ROAS for each line.
- Compare each campaign's ROAS against the right break-even figure.
- Shift budget toward the highest contribution per ad dollar, and watch whether it holds as you scale.
We build this reporting for online stores as part of our ecommerce growth work.