The most common Google Ads question from small business owners is how much they should spend. It is also the question with the most unsatisfying answer: it depends. Not because that is a convenient way to avoid committing, but because the right budget genuinely varies enormously depending on your industry, your location, your goals and the competitiveness of the keywords you are targeting.
When we set up Google Ads management for a client, what we give them are the principles that determine whether a budget is sufficient to work, and the warning signs that tell you a budget is being wasted.
The minimum effective budget
Google Ads works on an auction system. You bid against other advertisers for position in the search results for specific keywords. In a competitive market, a keyword like emergency plumber London might cost fifteen to thirty pounds per click. In a less competitive market like garden fencing North Wales, the same click might cost one to three pounds.
A budget that is too small to win competitive keyword auctions consistently will result in your ads appearing infrequently, generating insufficient data to optimise effectively, and delivering poor results. As a rough guide, a monthly Google Ads budget below three hundred pounds is unlikely to generate meaningful results in any market with genuine competition. In high-competition sectors like law, finance, home improvement or insurance, meaningful results typically require a minimum of one thousand pounds per month.
How to calculate what your budget should be
Start with what a new customer is worth to your business. If a new customer is worth five hundred pounds in lifetime revenue and your conversion rate from enquiry to customer is 30 percent, you need approximately three enquiries to get one customer. If your cost per click is three pounds and one in twenty clicks converts to an enquiry, you spend sixty pounds in clicks to get one enquiry. Three enquiries cost one hundred and eighty pounds. The customer is worth five hundred pounds. The maths work.
Run this calculation for your own numbers. If a customer is worth five hundred pounds and Google Ads would cost you three hundred pounds to acquire one, the return is clearly acceptable. If a customer is worth fifty pounds and it would cost you ninety pounds to acquire them, Google Ads is the wrong channel at that price.
How to avoid wasting your budget
The most common ways small businesses waste Google Ads budget are: targeting too broad a keyword set, failing to add negative keywords to exclude irrelevant searches, sending ad traffic to a homepage instead of a dedicated landing page, and running ads without proper conversion tracking in place — the same mistake behind ads that get clicks but no enquiries.
If you cannot measure what your ads are generating in terms of actual enquiries or sales, you cannot optimise them. Setting up conversion tracking correctly before spending a pound is non-negotiable.
What a well-managed budget actually looks like
A well-managed Google Ads account focuses on a tightly defined set of high-intent keywords, uses negative keywords aggressively to exclude irrelevant traffic, sends clicks to a dedicated landing page designed specifically for that ad, and tracks every conversion. Spend is reviewed weekly and shifted toward the campaigns, ad groups and keywords that are generating the best return.
If your current Google Ads is not being managed this way, budget is almost certainly being wasted regardless of how much you are spending.
