Budget enough to generate a useful test without risking money the business cannot afford to lose. For a cost per click campaign, work backwards from customer value and a realistic conversion range; do not begin with a competitor's daily budget or a universal "minimum".
Define the commercial ceiling
Decide what a new customer is worth after direct costs and how much of that contribution you are prepared to spend on acquisition. If one sale contributes £300 and the business can spend one third of that to win the customer, the target acquisition cost is £100. This is an internal decision, not an ad-platform benchmark.
For lead generation, multiply the target customer cost by the percentage of qualified leads that become customers. If one in four qualified leads closes, a £100 customer target supports roughly £25 per qualified lead. Use conservative assumptions when the data is new.
Translate the target into clicks
Estimate a click-to-qualified-lead range and CPC range using historical data, Keyword Planner and comparable campaigns. Build low, expected and high scenarios:
Expected leads = budget ÷ average CPC × landing-page conversion rate
Then apply the sales qualification and close rates. A range prevents false precision; a forecast is a decision tool, not a promise.
Set a learning threshold
Choose the smallest budget likely to produce enough relevant traffic to reveal obvious problems in targeting, message and landing-page experience. Very small tests can tell you that the setup is broken, but they cannot reliably prove long-term profitability.
Write the decisions in advance: pause for tracking failure, revise when search terms are irrelevant, and expand only when qualified outcomes approach the target. This makes the test disciplined rather than emotionally extended.
Convert monthly control into platform settings
Google Ads uses an average daily budget. For most campaigns, its official spending-limits guidance says daily spend can reach twice the average daily budget, while the monthly spending limit is generally 30.4 times that average. Use the current budget report and billing settings rather than assuming every day will spend the same amount.
Keep the first test narrow
Start with the highest-intent audience, one primary conversion and a landing page designed for the query. Reserve part of the total budget for changes after the first findings instead of committing everything to the initial setup.
This forecasting view approaches the question differently from our broader digital marketing budget guide. Digital Marketing in Practice teaches the campaign and measurement skills needed to turn a budget into a controlled learning plan.