“We doubled the ad budget, but enquiries went up by only a fifth. Where is the rest?” This is one of the questions clients ask us most often. It feels like there is a mistake somewhere, or that the contractor isn’t pushing hard enough. In reality, in most cases this is just how advertising works: each next pound or dollar usually brings in a customer at a higher price than the previous one.
First, the limits of this text. We don’t give exact numbers for “how much more expensive it gets”: they depend on the niche, the city and the season, and Google’s help has no such figure. What follows is an explanation from our practice, and where Google itself says something, we refer to it. We checked Google’s help on 7 October 2026.
What happens when the budget grows
What it is. In our experience, ads first reach the people who are easiest and cheapest to “catch”: those who are already searching for exactly your service, at a convenient time, on queries where you are strong. These are your cheapest customers. When you raise the budget, the ads are allowed to show more often and in less favourable places.
According to Google’s help, when the average daily budget is lower than what is needed to cover all available traffic, the campaign gets the status “Limited by budget”: ads are shown less often and you lose some impressions, clicks and conversions. So a bigger budget really does open up more traffic, and that is good. But this extra traffic is no longer as profitable.
Why it gets more expensive. The mechanism, as we see it, is this. To bring in more people, the ads show you higher and more often. And where there are more competitors, bids are higher. The impression gets more expensive, the click gets more expensive, and in the end the enquiry gets more expensive. This is not a settings mistake, just the normal rise in the cost of each next customer.
An illustrative example (not statistics). Before: 10,000 per month and 50 enquiries, that is 200 per enquiry. After: 20,000 and 60 enquiries. Enquiries are up 20 %, but each now costs about 333. What matters to the business isn’t that the budget doubled but whether it is still worth buying an enquiry at the new price.
What a sharp jump risks
If you raise the budget in one jump, you can’t see where exactly the cost per enquiry started to break. You doubled it, enquiries are a little higher, and it’s unclear: is it the season, a new promotion, or already the limit? Besides, Google’s automated bidding strategies need time to calibrate. According to Google’s help, they may need a few “conversion cycles” (the time from click to enquiry), typically one or two, and the algorithms keep learning even after the learning status has disappeared. Note that Google doesn’t list a budget change on its own among the triggers for learning, but a jump in spend changes the conditions the strategy works in.
What to do: advice from practice
This is not a Google rule but our own practice, and that is how we present it.
- Raise the budget in steps. We add 15–20 % at a time, not double.
- For two weeks, watch the cost per enquiry, not the number of enquiries. The number of enquiries usually goes up, and that proves nothing yet. What matters is whether the price holds.
- If it holds, add more. If the cost per enquiry stays within a range that works for you, take the next step. If it jumps, stop, go back to the previous budget and find out why.
There is no single figure for the step. Practitioners advise differently: from 5-10% to 10-20% at a time, and some about 30% every few days. Google’s official help gives no recommended step for budget changes: the pages on campaign budgets and on the learning period of automated bidding contain no percentage, only a note that the average daily budget can be changed at any time.
We take two weeks not from Google’s help but because, with a small number of enquiries, the figures over a shorter period are still too shaky. If an enquiry comes in once every few days, it is worth waiting longer.
When raising the budget makes sense and when it doesn’t
It makes sense to raise it when two conditions are met at once. First, the campaign is “limited by budget” and the current cost per enquiry suits you. Second, you are sure enquiries are counted correctly: otherwise you will pay more for “enquiries” that don’t actually exist.
Don’t raise the budget if enquiries aren’t set up properly yet, if the site handles requests badly (the form doesn’t send, the phone isn’t answered), or if your sales team can’t keep up with what already comes in. Extra money would then only increase the losses. Fix that first, then raise the budget.
Also note that there is a limit on your side too: whether you have the capacity to serve more customers. If not, doubling the budget won’t help, however many enquiries it brings.
When the problem isn’t the money
The “Limited by budget” status doesn’t necessarily mean the budget is what’s missing. Below is what Google Ads practitioners in the industry recommend checking, not our own statistics.
You may be hitting the ceiling of demand. If money was added, a click got more expensive, and the number of clicks didn’t grow, that is simply how many people are searching for your service. This is the “demand ceiling”. A bigger budget won’t help here: you need new search queries, a wider area or a wider range of products or services.
You may be losing on the ad, not on the money. Impressions are lost for two reasons: the budget runs out, or competitors beat you on ad rank. The first is cured with money, the second isn’t. Ask your contractor how many impressions were lost to budget and how many to rank.
The enquiries may have grown because of the season. At the peak, demand grows by itself, and the budget deserves less credit than it seems. A budget for a season is raised in advance, a few days before demand grows, not in the middle of the peak.
Don’t switch the campaign off in a panic. After a budget change the system recalculates its forecasts, and the cost per enquiry can swing for a few days. Practitioners consider switching a campaign off at that moment a typical mistake.
What to ask your contractor
- What is our cost per enquiry now, and what was it before the budget increase?
- Are the campaigns currently “limited by budget”? Where can we see that and how much are we losing?
- What counts as an enquiry? If it is a click on a phone number, the cost per enquiry may be false: more in the article on three checks for Google Ads.
- What is the next budget step, and by which indicator will we decide that we can add more?
Where to look
In Google Ads: Campaigns → Campaigns. The table has a “Status” column; if it says “Limited by budget”, the campaign isn’t getting all the available traffic (Google’s help explains the status). Look at the cost per enquiry in the cost per conversion column, but only if conversions are set up correctly: in Goals → Conversions, check what exactly is being counted. Another common reason why spend doesn’t match expectations is described in the article why Google Ads spends more than your daily budget.
Summary
A budget twice as large almost never brings twice as many customers: the ads have already taken the cheapest part of demand, and after that each customer costs more. That is normal if you watch the cost per enquiry and raise the budget in steps. Keep three things in mind:
- we raise the budget by 15–20 %, not in one jump;
- for two weeks we look at the cost per enquiry, not at their number;
- if the price holds, we add more.
You can read how we run campaigns and budgets in the search advertising and Performance Max sections.
Want a free audit of your Google Ads account? Send us a request — we will look at your account, tell you what your cost per enquiry is now and whether raising the budget makes sense.