Most paid advertising budget advice is some version of “spend 5 to 10% of revenue.”
That’s not useful. A 7-figure DTC brand with 35% margins and a 90-day payback window has completely different paid economics than an 8-figure B2B SaaS with 75% margins and an 18-month payback. They shouldn’t spend the same percentage of revenue, and they shouldn’t allocate it the same way.
So in this guide, I’ll walk you through the actual budget framework we use with scaling clients. The math behind it, the channels, and how to decide what’s enough vs too much.
The first question: what’s your payback target?
Before you can decide how much to spend, you need to know how fast you need the money back.
Three patterns we see:
- Aggressive growth: 12 to 18 month CAC payback acceptable. Brand is venture-backed or has cash to deploy. Goal is market share.
- Sustainable growth: 6 to 9 month payback. Self-funded or PE-backed. Profitability and scale balanced.
- Profit-first: 3 to 4 month payback. Bootstrapped or cash-flow-sensitive. Every pound spent must return inside the working capital cycle.
Your payback target sets your budget ceiling. You can spend up to whatever your customer acquisition cost can be while still hitting that target.
The math: how much CAN you spend?
Simple formula:
Max CAC = Gross profit per customer in your payback window
If a customer generates £400 of gross profit in their first 6 months, and you want a 6-month payback, your max CAC is £400.
If you want a 3-month payback, your max CAC is whatever the customer generates in those 3 months. Maybe £200.
This is your ceiling, not your target. Aim for 70 to 80% of max as your target so you have headroom for paid CPM inflation, returns, and cohort decay.
The math: how much SHOULD you spend?
Once you have target CAC, the budget question becomes a volume question.
Monthly paid budget = Target CAC × Number of customers you want to acquire this month
Want to acquire 200 customers this month at a £100 CAC? You need £20,000 in paid budget, distributed across the channels that actually convert.
The mistake we see constantly: brands spending whatever feels comfortable rather than working backward from acquisition targets. Comfortable spend in growth-stage businesses is almost always under-investment.
Channel allocation in 2026
For a typical DTC brand at our client scale (£3M to £20M revenue), the allocation that works:
- Meta (Facebook + Instagram): 40 to 55%. Still the workhorse for most DTC. Particularly strong for prospecting; weaker for retargeting since iOS 14.
- Google (Search + Shopping + PMax): 25 to 35%. Captures bottom-funnel intent. PMax has eaten share from manual Shopping campaigns.
- TikTok: 10 to 20%. Lower CAC than Meta for many DTC categories, especially under-£50 AOV. Audience demographics still skew younger.
- YouTube: 5 to 15%. Underused as a direct response channel. Pre-roll + Performance Max for video work well for considered purchases.
- Other (Pinterest, Reddit, Snap, podcasts): 0 to 10%. Test budget. Don’t go heavy until validated.
For B2B, the allocation shifts:
- LinkedIn: 35 to 50%. Still the best B2B paid channel despite costs.
- Google: 30 to 40%. Bottom-funnel commercial intent is enormous in B2B.
- Meta: 10 to 20%. Better than people think for B2B reach, especially Facebook for over-40 decision makers.
- YouTube/programmatic: 10 to 20%. Awareness and retargeting layer.
How much to allocate to top vs bottom funnel
One of the most-common mistakes: 80%+ of budget on bottom-funnel demand capture.
This works in year one when you’re scraping every ready-to-buy prospect from competitors. By year two, you’ve saturated demand capture and growth flattens. CACs climb 20-40% as you fight for the same shrinking pool.
The brands that scale past £10M revenue maintain a roughly 40/60 split between demand creation (top funnel: brand awareness, considered content, broad audience) and demand capture (bottom funnel: search, retargeting, lookalikes).
The 40% top-funnel investment doesn’t show up in last-click attribution, which is why most CFOs cut it first when revenue dips. That’s how brands get stuck in CAC inflation.
How to test new channels without burning budget
Three rules:
- £3,000 minimum spend over 14 days to give the channel enough data to optimise
- One creative concept, three variations. Not 20 ads spread thin.
- One conversion event being optimised. Don’t try to optimise for purchases AND signups in the same campaign.
Most channel tests fail because brands underfund them by 60-80% and then conclude “the channel doesn’t work for us.” Reality is they never gave the channel enough data to find their audience.
When to scale spend up
Don’t scale on a single week of good results. The signal is noisy.
The threshold we use:
- 4 weeks of stable CAC at or below target
- Conversion rate consistent (not driven by one weird week)
- Audience saturation index below 50% (room to grow before audiences get tired)
When all three hit, you can confidently 1.5x to 2x spend on the winning campaigns. More than 2x usually breaks the algorithm’s optimisation; ramp gradually.
When to cut spend
The hardest decision and the one most marketers get wrong.
The signal isn’t “this campaign isn’t profitable this week.” The signal is:
- 3 consecutive weeks of CAC drift above target
- Creative-fatigue indicators (CTR halving, frequency over 4)
- Cohort LTV from this channel underperforming the platform-reported metrics
When all three hit, cut. Not before, not after. Reactive cuts based on weekly fluctuations are how you kill scaling campaigns prematurely.
Pulling it together
For most scaling brands at £3M to £20M revenue, paid advertising spend should land in 8 to 18% of revenue. The exact number is determined by:
- Your payback window
- Your gross margin
- How much top-funnel investment you’re sustaining
- How fast you want to grow
Generic “spend X% of revenue” advice ignores all four. Build the budget from your unit economics outwards, not from a percentage downwards.
And remember the worst budget mistake of all: under-spending in periods when CAC is healthy. You should always be testing how much MORE you can profitably spend. The brands that win are the ones that find the ceiling, not the ones that camp comfortably under it.