How to Calculate ROAS: Why Your ROAS Doesn't Show What You Keep

ROAS is the metric every ad service provider shows you first. It's useful, but it only measures half the journey. It answers how well your ads sell. It doesn't answer what the whole machinery around them costs you. And that's exactly where it's decided whether advertising pays off for you.

How to Calculate ROAS: The Formula

The formula is short:

ROAS = revenue from ads ÷ ad spend

If you spend €3,000 on Meta ads in a month and can attribute €15,000 in revenue to them, your ROAS is 5. What matters is that you take revenue and ad spend from the same period and cleanly attribute which revenue comes from the ads.

What Counts as Ad Spend and What Doesn't

ROAS only includes the money that goes to the platform. It doesn't include:

• your agency's monthly retainer,
• costs for videos and images,
• percentage surcharges or budget fees,
• one-time setup costs.

That's not a flaw in the metric; it's its purpose. But it means two providers with the same ROAS can cost you completely different amounts.

The Blind Spot: Costs Outside the Ad Budget

Imagine you have a fixed amount for two years. Part of it goes to the service provider, the rest into ads. The more the provider gets, the less ad budget remains. The ROAS stays the same, but it works on a smaller sum.

That's why we look at two more values:

• Revenue per euro spent: revenue divided by everything you pay, i.e. ads plus service provider.
• What you keep: revenue minus everything you pay. That's not profit yet, but it shows how much room is left for cost of goods, team and profit.

Worked Example: Same ROAS, Same Spend, Different Result

How We Run the Comparison

Both sides invest exactly the same total spend. On the Plaith side, it consists of your own ad budget, the setup fee, the package price, the budget fee and, if selected, the Booster. On the classic side, we subtract the cost of management and videos from the same amount. The basis is the benchmark from the expert report (Start €1,885.96, Growth €3,485.39, Scale €9,083.40 per month). The rest goes into ads. We don't include an agency setup fee there. Agency surcharges on the ad budget (for example 5% on everything or 10% on the portion above €1,000 per month, expert report section 4.1) are deliberately not included, so Plaith's lead is, if anything, larger.

Our example S3: Growth package, €3,000 of your own ad budget per month, a Booster with a one-time payment of €10,000, 24 months, ROAS 5 as an assumption.

Both sides pay €128,115. The ROAS is identical. Yet Plaith shows €480,000 in revenue, the classic model €222,328.20. The only reason is the ad budget: €96,000 vs. €44,465.64. With Plaith, €24,000 of Booster credit is added to your own budget, and €56,115 goes to the service provider instead of €83,649.36.

So every euro you spend turns into €3.75 of revenue with Plaith, versus €1.74 with the classic model. What you keep: €351,885 vs. €94,213.20.

What the Booster Is

The Booster is an add-on module. Your ad budget then runs through Plaith instead of going directly to Meta. We pass our purchasing terms on to you as an ad budget package: for a one-time payment, you get one tenth of it as additional ad credit every month for 24 months, on top of your own budget. That turns €10,000 into €1,000 per month and €24,000 over the term. The credit is only valid with an active Plaith contract, is non-transferable, is not paid out in cash and is only used for ad delivery. If you cancel, you get the one-time payment back minus the credit already delivered, with a minimum of €0. If the platform's purchasing terms change, Plaith can end running packages with 30 days' notice; the same refund rule then applies. You'll clarify the exact terms in a call.

Cross-Check Without the Booster

The gap doesn't depend on the Booster. To show you, here's the same scenario without a Booster (S4):

Even without a Booster, there's a gap of €197,271.80. It comes solely from the fact that more money goes into ads at the same spend.

What Happens If ROAS Is Lower?

ROAS is the biggest uncertainty in any ad calculation. That's why we show the same scenario at ROAS 3, 4 and 5:

Two things stand out. First, "What you keep" shrinks sharply on both sides when ROAS drops. Second, the gap between the two sides remains, because it comes from costs. At ROAS 3, the classic model leaves only €5,281.92, Plaith €159,885.

What ROAS Tells You and What It Doesn't

ROAS helps you compare campaigns with each other. If it rises, your ads are selling better. For the question "Which service provider is worth it for me?", you need more:

1. Set your total spend: What do you want to spend in total over a given period?
2. Break down the costs: How much goes to the service provider, how much to the platform?
3. Assume the same ROAS: That way you compare cost structures, not promises.
4. Calculate what you keep: revenue minus total spend.
5. Check your margin: Only with your gross profit does "What you keep" tell you something about profit.

Common ROAS Mistakes

• Too short a period: One good month says little about a year.
• Double-counted revenue: When several channels claim the same purchase, ROAS looks better than it is.
• Forgotten costs: Agency, videos and fees don't show up in ROAS.
• Confusing revenue with profit: ROAS 3 can mean a loss if your margin is low.

What You Get When You Look Beyond ROAS

Your dashboard shows a good ROAS, but less money lands in your account than you expect. You want to know why. You don't want to become an accountant to find out.

With a second number next to ROAS, you see which part of your spend is actually working for you.

Here's what the second number gives you:

• Clarity in a single number. Revenue per euro spent shows the whole machinery. In S3, at the same ROAS, that's €3.75 with Plaith and €1.74 with the classic model.
• The right lever. You can tell whether you need to work on your ads or on your costs. Those are two different jobs.
• Better questions for providers. You no longer ask only about ROAS. You ask about what's left after all costs.

We treat ROAS as an assumption in every calculation. It says nothing about your margin.

Objections, Answered Honestly

If you read ROAS differently, you usually have a good reason. Here are three natural objections:

"My ROAS is high, so everything's working."

ROAS measures your ads, not the machinery around them. A high value can be eaten up by high service provider costs. So subtract all costs before you judge.

"Setting ROAS equal on both sides is unfair."

We set it equal so that only costs make the difference. If a provider promises you better ads, they should prove it. We never assume a higher ROAS for one side.

"What I keep is my profit, isn't it?"

No. "What you keep" is revenue minus ad budget and service provider costs. Cost of goods, staff and taxes are still missing. Only after that do you know what you earn. The article Ad Costs and Contribution Margin shows how.

Frequently Asked Questions

How do I calculate ROAS?

Divide the revenue you can attribute to your ads by the ad spend in the same period. €15,000 in revenue from €3,000 in ad spend gives you ROAS 5.

What's the difference between ROAS and what you keep?

ROAS divides revenue by ad spend. "What you keep" subtracts everything you pay from revenue, including agency, videos and fees. Only then do you see how much room is left.

What's a good ROAS?

That depends on your margin, not on a universal number. You'll find more in the article Is a ROAS of 3 Good?. The rule: the lower your gross margin, the higher your ROAS needs to be.

Further Reading

These articles go deeper on individual points:

• ROPS: The Metric That Shows What Your Ad Service Provider Delivers
• Is a ROAS of 3 Good? Why the Answer Depends on Your Margin
• Ad Costs and Contribution Margin: How to Check Whether Your Ads Pay for Themselves

Run Your Own Scenario

Take your current ROAS and check what's left after all costs. Then open the **Plaith calculator on plaith.ai**. Enter your package, your own ad budget per month and, if you like, a Booster. Then choose a conservative ROAS assumption, for example 3. You'll instantly see the ad budget, the cost paid to Plaith and the ROPS for your case. The same applies there: worked example, no guarantee.

Sources

• Expert report on the costs of Meta management and videos with real people, version of October 5, 2026: sample of documented offers, not a market study. Benchmark = average of the four Meta management packages (€1,086.25) plus videos at the average price of 224.42 US dollars, converted at 1.1225 USD per euro (sections 4.1 on p. 4, 5.4 on p. 11, 6.3 and 6.4 on pp. 14 to 17).
• Plaith's own calculations (as of October 6, 2026): package prices, budget fee, Booster and all scenario numbers in this article, recalculated exactly.