In most American categories, a $500 monthly Google Ads budget and no Google Ads budget produce roughly the same number of customers.
One of them shows up on your card.
That is the uncomfortable middle of this question, and almost nobody says it out loud, because the platform has no interest in telling you your budget is too small and neither does anybody who would manage it for you.
So here is how to work out your own floor, meaning the smallest budget that can produce a result at all. I wrote separately about the maximum affordable click, which is your ceiling. This is the other end. You need both numbers, and if the floor sits above the ceiling, the channel is closed to you and that is worth knowing in an afternoon rather than a quarter.
Why there is a floor at all
Automated bidding needs roughly thirty conversions in a thirty day window before it performs reliably, and fifty for target ROAS.
Below that the system never leaves the learning phase. Performance stays volatile, costs stay high, and every change you make resets a process that had not finished anyway. You are not running a small campaign. You are running a different thing that does not work.
The floor is therefore not a number Google publishes or a number you choose. It is set by your category’s click price and your own conversion rate, and for a lot of US businesses it is considerably higher than they expect.
The calculation, for somebody who has never run ads
If you already have data, use your own cost per lead and multiply by thirty. Done.
If you are starting from nothing, you can still get there with two numbers.
Your category’s average cost per click. The 2026 all-industry average on Search is $5.42. Home and home improvement runs around $8.33. Attorneys and legal services average $9.87. Find yours in any of the published benchmark round-ups.
Your landing page conversion rate, meaning the share of clicks that become an enquiry. The cross-industry average is about 8%. If you have never measured it, use 5% and be pleasantly surprised later.
Then: category cost per click, times clicks needed per conversion, times thirty.
A home services business at $8.33 a click converting 8% of them needs about 12.5 clicks per enquiry, so roughly $104 per enquiry, so a floor near $3,125 a month.
A law firm at $9.87 a click converting 5% needs 20 clicks per enquiry, so about $197 each, so a floor near $5,900 a month.
An ecommerce store at $2 a click converting 2% of them needs 50 clicks per sale, so $100 a sale, so a floor near $3,000 a month.
Those are media budgets, before any management fee.
Sit with those numbers, because the gap between them and what most small businesses imagine is the whole problem. A floor in the three to six thousand dollar range is normal in the United States, and the business planning to “try it with a thousand” is planning to buy nine conversions a month and conclude the channel does not work.
The daily budget is not a cap, and people set it wrong
Two mechanics worth knowing, because both cause unnecessary panic.
Your average daily budget is an average. On any given day a campaign may spend up to twice it, to take advantage of traffic Google expects to convert. It compensates on other days by spending well under.
What is capped is the month. You will not be charged more than 30.4 times your average daily budget, that figure being the average number of days in a month.
Two consequences. Do not panic at a single day’s overspend and do not switch the campaign off because of it. And when converting a monthly budget into a daily one, divide by 30.4 rather than by 31 or by 30, because that is the number the system actually uses.
When the floor is above what you have
This is where most readers are, so it deserves a real answer rather than a suggestion to find more money.
Narrow until the floor comes down. The floor is a function of your click price and your conversion rate, and narrowing improves both. One service instead of five. Exact match on the twenty terms that genuinely describe what you sell. One city rather than a state. Business hours only, if nobody answers the phone at night.
A tightly drawn campaign has a higher conversion rate than a broad one, which cuts the clicks needed per conversion, which cuts the floor directly. Narrowing is not a compromise here. It is the mechanism.
Fix the landing page before you fix the bidding. Doubling your conversion rate halves your floor. There is no bidding strategy that delivers a change of that size, and the work costs media budget of exactly zero.
Count the right conversion. If you are optimizing toward completed sales at a 2% rate, the system sees almost nothing. Optimizing toward a qualified enquiry, which happens more often, gives it more to learn from. Only do this if the enquiry is a genuine business outcome, because feeding the system a soft conversion produces a campaign that is excellent at generating things you do not want. I went through what happens when you feed the wrong signal separately.
Or do not run ads. If your category costs $9.87 a click and you have $800 a month, paid search is not your channel this year. Spend it on the things that convert the traffic you already get, and revisit when either the budget or the conversion rate has changed.
The check that tells you whether budget is even your problem
One report settles this and hardly anybody opens it.
In your campaign columns, add Search lost impression share (budget). It tells you what share of available impressions you missed specifically because your budget ran out.
If that number is high, budget is genuinely your constraint and more money buys more volume.
If it is low, your budget is not the binding constraint. You are already showing for most of what you are eligible for, and the problem is elsewhere: your keywords are too narrow, your quality scores are poor, or your page is not converting. Adding money to that campaign buys you nothing, and it is the single most common misdiagnosis I see.
Check that before you increase spend, every time.
Before lunch
Three things, about thirty minutes.
Look up your category’s average cost per click and write it down. Multiply by the clicks you need per enquiry, then by thirty. That is your floor, and it is the number the rest of the conversation depends on.
Compare it against your maximum affordable click from the other calculation. If the floor is above what a customer is worth to you, stop here and go and improve the thing that determines that value.
If you are already running ads, add the lost impression share to budget column and find out whether money is actually your constraint.
None of this is advice about how to run campaigns. It is the arithmetic that decides whether running them is a sensible use of the money at all, and it takes half an hour to settle a question that otherwise takes a quarter and a few thousand dollars.
My notes on performance marketing cover what happens after the numbers clear. If you’d like a second read on your own figures, drop me a line on email, WhatsApp or LinkedIn and we can have a quick chat. I’m contracted full time so this isn’t a pitch.