There's no universal budget figure — work backwards from your own numbers: divide the leads or sales you want per month by your website's conversion rate to get the clicks required, then multiply by your average cost-per-click. My management fee (from £300/month) sits on top of that media spend.
Book a free strategy callYou’ll see the same advice everywhere: spend 5-10% of revenue on marketing, or start with £1,000-£2,000 a month and see how it goes. I understand why people reach for a rule like that — it feels safer than an unknown number — but it’s the wrong way round. It tells you nothing about whether that budget will actually buy enough clicks to reach your goal.
Two businesses with identical revenue can need wildly different Google Ads budgets. A niche B2B service with a £30 cost-per-click and a handful of monthly searches needs a different budget entirely to a local trades business with £3 clicks and thousands of searches. A generic percentage-of-revenue figure ignores both of those realities completely — it’s not connected to your market at all.
For a lead-generation business, budget is really a question of what you can afford to pay per lead and still make the numbers work once your sales process converts a proportion of those leads into paying customers. The constraint is often less about the ad spend itself and more about how many new enquiries your team can actually handle well — there’s no point buying more leads than you can follow up on properly.
For ecommerce, the calculation runs through margin rather than a fixed cost-per-lead ceiling: what return on ad spend do you need for a sale to be worth acquiring, given your product margins? There’s also a structural budget driver that lead-gen businesses don’t have — catalogue breadth. A Shopping or Performance Max campaign covering hundreds of SKUs needs enough budget spread across that catalogue for Google’s systems to gather meaningful signal on which products actually sell, not just the handful of obvious bestsellers.
This is one of the most common ways I see Google Ads budgets fail, and it rarely gets discussed openly: a budget that’s too thin to generate enough clicks and conversions simply never produces the data needed to optimise. Google’s automated bidding relies on conversion volume to learn what’s working — a campaign starved of that volume stays stuck, decisions get made on tiny, noisy samples, and it’s genuinely impossible to tell whether the strategy is wrong or the account just hasn’t had a fair chance yet. If your realistic budget can’t buy enough clicks to reach a meaningful number of conversions in a sensible timeframe, that’s worth knowing before you start, not three months in when you’re trying to work out why nothing’s clear.
Your ad spend and my management fee are two separate things, and it’s worth being clear on both. Ad spend goes directly to Google — I don’t mark it up or take a cut of it. My fee is for managing the account: strategy, structure, bidding, tracking, optimisation and reporting.
My management fee starts from £300/month, which covers ad spend up to £3,000/month. Above that, the fee is 10% of your ad spend. So a £4,500/month ad spend works out at a £450/month management fee. When you’re sizing a total budget, it’s worth adding the fee on top of whatever media spend your own calculation above points to, rather than treating the whole figure as one pot — that way you know exactly what’s buying clicks and what’s buying the management of them.
Start with the calculation, not a round number pulled from habit. Work out the media budget your target genuinely requires, add the management fee on top, and treat that combined figure as the honest cost of finding out whether Google Ads works for your business — not as a maximum you’re hoping to avoid. If that number is higher than you expected, it usually means the market you’re in has expensive clicks or low search volume, and that’s useful information in itself: it might point you towards a narrower campaign focus, a longer runway before judging results, or a conversation about whether Google Ads is the right channel at all right now.
There isn’t a fixed minimum that works for everyone — it depends entirely on your cost-per-click and how many conversions you need before you can judge performance. The steps above (target outcome ÷ conversion rate × CPC) will give you a figure specific to your own market rather than a generic starting point.
Underspending can happen for several reasons — tight targeting, low bids relative to competition, or genuinely low search volume for your terms — but a budget that’s too small to generate meaningful conversion volume is a common contributing factor. It’s worth diagnosing rather than assuming, since the fix is different depending on the cause.
The logic behind the number differs even when the figures happen to be similar. Lead gen is usually bounded by what you can afford per lead and how many enquiries your team can handle well. Ecommerce is usually bounded by margin and target ROAS, plus the need for enough budget spread across your product catalogue for Shopping or Performance Max to learn which products sell.
Yes. Ad spend is paid directly to Google — there’s no markup on it. My fee is separate: from £300/month, covering ad spend up to £3,000/month, then 10% of spend above that. A £4,500/month ad spend, for example, works out at a £450/month management fee.
If you’re seeing very few conversions per month and performance seems to swing wildly rather than trend in a clear direction, that’s a sign there isn’t enough volume for Google’s bidding systems (or you) to draw reliable conclusions yet. It’s worth reviewing whether the budget realistically supports the conversion volume your target requires.
Both have a place. If the calculated figure is a genuine stretch, it’s reasonable to phase up as confidence builds. But cutting the number too far below what the maths actually requires risks landing back in the “not enough data” problem — a budget that’s too thin to reach meaningful conversion volume rarely tells you anything useful, however long you leave it running.
I'll look at your market, your numbers, and what you're trying to achieve, and give you an honest read on the budget that's actually required — not a rule of thumb. Book a free strategy call and we'll work it out together.
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