SMB AI Marketing Budget: How Much to Spend and Where

Do not create an "AI budget"

A separate line for AI encourages buying tools for their own sake. The useful question is the old one: how many customers do you need, and what can you afford to pay to win each one? AI changes how the money is spent, mostly by moving cost from production hours towards review and judgement. It does not change how the total should be set.

Many small firms are still early here. Published summaries of the Office for National Statistics' survey data describe AI use among UK businesses rising since 2023, with relatively few users describing their use as extensive; read the current ONS release for the figures. There is no reason to budget as though you are behind.

Step 1: Set the total from the outcome

Illustrative example with hypothetical round figures, for a service business.

• • Target new customers per month: 10
• • Gross profit per customer over the first twelve months: £1,200
• • Allowable acquisition cost: a third of first-year gross profit, so £1,200 ÷ 3 = £400 per customer (the fraction is a policy choice; a business with strong retention or spare cash may allow more)

Monthly marketing budget: 10 × £400 = £4,000.

This number is a ceiling, not a spending target. Spending less to get the same customers is the point of the exercise.

Step 2: Split it by what the funnel needs

Divide the total across three lines. The split below is an illustration, not a rule.

Illustrative split of a £4,000 monthly budget

Line	Amount	What it buys	How AI changes it
Media	£2,400 (60%)	Paid search and social, sponsored placements	Faster creative and audience testing; platform bidding already uses machine learning
People or managed service	£1,300 (32.5%)	Strategy, production, review, reporting	Fewer production hours per asset; more of the cost is judgement and review
Tools	£300 (7.5%)	Software subscriptions and usage	A few well-chosen tools, not one per task

A business that sells mainly through search engine optimisation, referrals or outbound will put less into media and more into people. The totals from Step 1 still hold.

Step 3: Check the funnel can deliver it

Now test whether £2,400 of media can plausibly produce 10 customers.

• • Lead-to-customer rate, from your own records: 20%
• • Leads needed: 10 ÷ 20% = 50
• • Media cost per lead the plan requires: £2,400 ÷ 50 = £48

Compare that with the cost per lead you actually achieve. Suppose your recent campaigns deliver leads at £80. Then £2,400 buys 2,400 ÷ 80 = 30 leads, which at 20% is 6 customers, not 10.

You now have a clear choice, and it is a business decision rather than a marketing one:

1. • Lower the target to 6 customers at the current budget;
2. • Raise the budget, if the economics allow: 50 leads at £80 is £4,000 of media alone, which with people and tools breaks the £400 ceiling;
3. • Fix the funnel: improve the conversion rate from lead to customer, or the cost per lead, before adding money. This is often where AI-assisted work earns its keep, through more landing page and creative tests per month.

To see the full cost per lead, qualified lead and opportunity including people and tools, use the cost-per-lead calculator in AI for B2B Marketing ROI.

Step 4: Translate the media line into platform settings

Platforms work in daily budgets. In Google Ads, the monthly charge for a campaign is capped at 30.4 times its average daily budget, and on any single day it can spend up to twice the daily figure to follow traffic. So a £2,400 monthly search budget becomes an average daily budget of £2,400 ÷ 30.4 = £78.95. Expect individual days to vary around that.

Step 5: Review quarterly and move money on evidence

Hold the split for a quarter, then move money toward the line that produced customers most cheaply. Moving it monthly reacts to noise. For how to judge which channel deserves the next pound, see Optimising Marketing Spend With AI. If you are pre-revenue with a fixed pot rather than a monthly budget, AI Marketing Strategy for Startups: Your First GBP 5K is the better guide.

Common budgeting mistakes

• • Budgeting as a percentage of revenue only. It ignores whether your funnel can turn money into customers at a price you can afford.
• • Buying tools before deciding the work. Subscriptions accumulate; each one needs someone's time to use well.
• • Forgetting review time. AI reduces drafting time, not the need to check what goes out under your name.
• • Using the best month's conversion rate. Budget on a two or three quarter average.

FAQ

What share of revenue should a small business spend on marketing?

There is no universal figure. Working back from target customers and allowable acquisition cost gives a budget tied to your own economics, which is more defensible than a percentage borrowed from elsewhere.

How do I choose the allowable acquisition cost?

Start from first-year gross profit per customer and decide how much of it you are willing to spend to win the customer. The fraction depends on retention, cash and risk appetite.

Should I budget for AI tools separately?

Put them in the tools line with everything else and justify each by the work it supports. A separate AI line tends to grow without a clear outcome attached.

Why can Google Ads spend more than my daily budget on some days?

Google lets a campaign spend up to twice its average daily budget on a given day to follow traffic, while keeping the month within 30.4 times the daily figure.