Most marketing budgets are set the same way: take last period's number and adjust it up or down by a feeling. It's fast, and it's also disconnected from the two things that should actually decide the number — what you're trying to earn, and what your margin can afford to spend to get there.
A budget built from the goal backwards answers a different, more useful question: given this revenue target and this margin, how much can be spent on ads before the extra spend stops paying for itself? That number is rarely close to "last year plus 10%."
This guide covers how to calculate a budget from a revenue goal, why marginal efficiency falls as spend rises even when average ROAS still looks healthy, how to find the point where more budget stops being worth it, how to split a total budget across channels and phases, and what More Nutrition changed to cut customer acquisition cost over 70% while growing revenue from paid social by 81%.
Admetrics is a marketing measurement and budget platform for ecommerce and DTC brands. We measure true marginal return by channel, independently of the ad platforms, and show the point at which additional spend stops earning its keep.
Key takeaways
- Ad budget = revenue goal ÷ target MER. A €300,000 goal at a target MER of 5.0 needs €60,000 of ad spend.
- Average ROAS hides marginal ROAS. The last €1,000 of spend in a campaign almost always returns less than the first €1,000; a healthy average can sit on top of a last euro that's already unprofitable.
- The budget check that matters: revenue goal × CM2 ratio − ad budget. If that's negative, the goal, discount or budget needs to change before the plan is final.
- A bigger budget doesn't have to mean worse efficiency, if attribution is trusted first. More Nutrition cut cost per new customer by over 70% and grew paid-social revenue 81% in 12 months by fixing what it measured before changing how much it spent.
- Split by phase, not just by channel. A proven Black Friday approach allocates roughly 5/80/5/5/5 across anticipation, pre-Black Friday, Black Friday, pre-holiday and holiday.
- Budget decisions should update weekly, not quarterly. A rolling budget that moves money toward what's still earning outperforms one fixed at the start and left alone.
Why "last year plus 10%" is the wrong starting point
An incremental budget inherits every assumption baked into last year's number: the margin was the same, the competitive landscape was the same, the channel mix still works the same way. None of those usually hold for an entire year, and Black Friday compresses a year's worth of change into one week of competition for the same inventory of ad impressions.
The alternative starts from two numbers you already have — a revenue goal and your margin — and derives the budget, rather than assuming it.
Setting the budget from the goal
Step 1: Orders needed = revenue goal ÷ expected average order value (after any planned discount)
Step 2: Ad budget = revenue goal ÷ target MER
Step 3: Check = (revenue goal × CM2 ratio) − ad budget
Step 3 is the one most budgets skip. It asks whether, after paying for the ads in step 2, there's still a positive contribution left over. If the answer is negative, one of the three inputs — the goal, the discount depth, or the target MER — has to move before the plan can work.
| Target MER | Ad budget (on €300,000 goal) | Contribution at 25% CM2 ratio | Contribution after ads |
|---|---|---|---|
| 4.0 (break-even) | €75,000 | €75,000 | €0 |
| 5.0 | €60,000 | €75,000 | €15,000 |
| 6.0 | €50,000 | €75,000 | €25,000 |
The same revenue goal produces three entirely different answers for "how much should we spend" depending on which MER target the budget is built around, and only one of those three leaves money on the table after marketing. This is the calculation the free marketing budget calculator runs automatically from your own goal, AOV and margin.
Average ROAS hides where the real limit is
A campaign reporting a 4.0 average ROAS sounds like a candidate for more budget. Average ROAS, though, blends the easy early spend with the harder later spend, and the two can look nothing alike.
Every acquisition channel has a response curve: spend rises, and so does revenue, but not at a constant rate. The first portion of the budget typically reaches the audience most likely to convert — people already close to a purchase decision. Each additional euro has to reach someone slightly less likely to buy, so the marginal return on that euro falls even while the campaign's average, blending the cheap early euros with the expensive later ones, can still look healthy.
| Spend tranche | Revenue from that tranche | Marginal ROAS (this tranche only) | Cumulative average ROAS |
|---|---|---|---|
| First €10,000 | €60,000 | 6.0 | 6.0 |
| Next €10,000 | €35,000 | 3.5 | 4.75 |
| Next €10,000 | €18,000 | 1.8 | 3.77 |
| Next €10,000 | €8,000 | 0.8 | 3.03 |
At €40,000 total spend, the campaign still reports an average ROAS of 3.03, which can look acceptable against a break-even of, say, 2.6. But the last tranche of that spend returned only 0.8, well below break-even — it is actively losing money, hidden inside an average that's still positive overall. The budget question isn't "is average ROAS above break-even"; it's "where does marginal ROAS cross below break-even", because every euro spent past that point is a euro that would have been better held back or moved to a different channel.
Finding where more spend stops paying
The practical version of this question, for a budget-setting conversation: at what spend level does the next euro into this channel stop clearing the break-even ROAS for the products it's selling?
- Plot recent spend and revenue in roughly even tranches (weekly budget steps work well) rather than relying on the campaign-level average.
- Calculate marginal ROAS for each tranche: the revenue added by that tranche, divided by the spend added by that tranche — not cumulative totals.
- Compare each tranche's marginal ROAS to your break-even ROAS for the products being sold at that discount.
- Set the ceiling at the tranche where marginal ROAS first drops below break-even, not where the average does.
This is close to what a marketing mix model does continuously and across every channel at once, rather than one spreadsheet tranche at a time: it estimates each channel's full response curve, including the diminishing-returns bend, so budget can be allocated to wherever the next euro still clears the bar, before that euro is spent rather than after.
Case study: More Nutrition cut CAC 70% before it changed how much it spent
The natural response to a plateau is to spend more. More Nutrition, the German sports nutrition brand, had a more basic problem first: it was optimising for platform-reported ROAS, on algorithms that favoured their own reported success over true incremental revenue, while manual media buyers had to log into each platform multiple times a day just to catch losing ads before they burned through budget.
Before More Nutrition could sensibly decide how much to spend, it needed to trust what spend was actually returning. Admetrics pulled data from over 13 ad platforms plus Shopify and offline retail, then reconstructed each customer's path with a U-shape multi-touch model crediting first touch, last touch and the touchpoints in between — replacing the platform's own, self-interested view of its contribution.
Within 12 months of that measurement foundation being in place: cost per new customer fell over 70%, new-customer rate grew more than 65%, average order value rose 19%, and revenue from paid social rose 81%, all while creative output rose roughly tenfold per week.
"Real attribution didn't just improve our measurement, it changed who we went after. Our new customer rate grew 65% while AOV climbed 19%, numbers we could finally trust and act on."
— Paul Keil, Team Lead Performance Marketing, More Nutrition
The lesson for budget-setting specifically: the size of the budget was not the constraint. The constraint was that nobody could tell, channel by channel, where the next euro was actually going — which is exactly the gap between average and marginal ROAS described above. Fixing that measurement gap, not the budget total, was what let More Nutrition direct spend toward customers worth acquiring rather than toward whichever platform reported the best number about itself.
Splitting the total budget
By channel
Once the total is set, allocate it where the response curve, not the historical split, says it still earns. A channel that took 40% of last year's budget because it took 40% the year before is not evidence it still deserves 40% — only this year's marginal returns are.
By phase, for Black Friday specifically
A commonly used structure splits the Black Friday period into five phases, roughly 5% anticipation, 80% pre-Black Friday, 5% Black Friday itself, 5% pre-holiday and 5% holiday. The heavy pre-Black Friday weighting reflects that costs rise sharply on the peak days themselves, so banking impressions and retargeting audiences in the cheaper run-up weeks is usually more efficient than trying to buy everything on the day.
| Phase | Typical share | Purpose |
|---|---|---|
| Anticipation | ~5% | Build retargeting audiences and early-bird interest before the sale starts |
| Pre-Black Friday | ~80% | The bulk of acquisition, at lower CPMs than the peak days |
| Black Friday | ~5% | Push on the day itself, largely to already-warm audiences |
| Pre-holiday | ~5% | Capture demand shifting toward gifting |
| Holiday | ~5% | Last-chance and delivery-deadline messaging |
Whatever split is chosen, set a separate cost ceiling per phase rather than one for the whole period — the break-even point moves with the discount depth each phase runs, so a ceiling calibrated for the pre-Black Friday discount will be too loose for the deeper cuts typically run on the day itself.
Rolling the budget instead of fixing it
A budget decided in October and left untouched through November ignores everything the campaign learns about itself along the way. A rolling approach checks performance against the ceiling set above on a regular cadence — weekly outside Black Week, daily or more often inside it — and moves the next tranche of spend toward whichever channel is currently furthest below its ceiling, rather than toward whichever channel the original plan allocated it to.
This matters more in Black Week than anywhere else in the calendar, because costs, competition and consumer behaviour all move faster during the week than any plan set in October could account for. Our Black Friday preparation guide covers the full timeline, including when to lock the initial budget and when to start rolling it.
Common mistakes
- Setting the budget from last period's spend instead of this period's goal. It carries forward every assumption that may no longer hold.
- Judging a channel on average ROAS alone. A healthy average can sit on top of a loss-making marginal euro.
- Trusting platform-reported ROAS when sizing the budget. As More Nutrition found, platforms can favour their own reported contribution; an independent, order-anchored view changes which channels look worth funding.
- Splitting budget by historical share rather than current response curve. Past allocation is not evidence of present efficiency.
- Using one Black Friday ceiling across the whole period. Break-even moves with the discount depth each phase runs.
- Fixing the budget at the start and not revisiting it. A rolling budget that responds to what's actually happening consistently outperforms a static one.
Marketing budget calculator
Try it with your own numbers: the free marketing budget calculator sets your ad budget from your revenue goal and margin, and shows the contribution left over after that spend. For the margin inputs, use the contribution margin calculator; for the discount-adjusted version, the discount profit calculator.
FAQ
How do you calculate a marketing budget from a revenue goal?
Divide the revenue goal by a target MER that sits above your break-even MER. A €300,000 goal at a target MER of 5.0 needs a €60,000 budget. Then check that revenue times your CM2 ratio, minus that budget, still leaves a positive contribution.
Why does average ROAS look fine while a channel is still inefficient?
Because the average blends cheap early spend with more expensive later spend. The marginal ROAS on the last euro spent can already be below break-even while the campaign-wide average is still comfortably above it.
Should I increase my budget before fixing how I measure it?
Usually not. More Nutrition's biggest gains — cost per new customer down over 70%, revenue from paid social up 81% — came from replacing platform-reported ROAS with independent, order-anchored attribution first, which then showed where the existing budget, and later more of it, was actually worth spending.
Should I split my Black Friday budget evenly across the week?
No. A common and effective approach weights roughly 80% of spend to the days before Black Friday, when costs are lower, with smaller allocations for anticipation, the day itself, and the days after.
How often should a marketing budget be revisited?
Weekly at a minimum, outside of peak periods; daily or more often during Black Week, when costs and competition move faster than any plan set in advance can anticipate.
Set your budget on real marginal return
Admetrics shows true marginal ROAS and POAS by channel and campaign, measured independently of the ad platforms, so budget decisions follow where the next euro still earns rather than where last year's plan, or the platform's own report, put it.
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