There is no universal minimum Google Ads budget, but there is a minimum for your category. It is set by what a click costs, how many clicks make a lead, and how much data the bidding algorithm needs to stop guessing.
The learning threshold
Smart Bidding wants roughly 30 conversions in 30 days per campaign to work well. If your cost per lead is $100, that is $3,000 a month. If it is $30, $900 does it. Below that threshold the algorithm is running on thin data and results swing wildly week to week.
You can still advertise below it — just use manual or maximise-clicks bidding and a much tighter keyword set until volume builds.
Work backwards from revenue
Decide how many new customers a month you want. Divide by your lead-to-customer close rate to get leads needed. Multiply by your expected cost per lead. That is your media budget — not a percentage of revenue pulled from a template.
Example: 5 customers, 25% close rate, 20 leads needed, $80 a lead, $1,600 a month.
Practical ranges by category
Local services: $1,500–$5,000 a month. Professional services and B2B: $2,500–$10,000. Legal, medical and high-value trades: $5,000–$20,000 because clicks are expensive. Ecommerce: starts lower but needs more to scale.
In the UK, divide the dollar figures roughly in half in less competitive regions.
Spend narrow before you spend wide
A small budget on one city and ten keywords beats the same budget on five cities and two hundred keywords. Depth first. Once one segment is profitable and stable, expand geography or service line, not both at once.
When to increase
Increase when your campaigns are limited by budget and cost per lead is at or below target. Raise by 20–30% at a time and wait a week — larger jumps reset the learning phase and results dip before they recover.
If you want a sanity check on what your current budget should be producing, start with an ad account audit.