Guide
Why Google Ads spends more than your daily budget
Your Google Ads budget is an average daily budget, not a daily cap. On a busy day a campaign can be charged up to 2 times it, and over a calendar month up to 30.4 times it. So a high day is normal. The month is what to watch.
The most a campaign can be charged
| Limit | Rule | At 100 a day |
|---|---|---|
| In one day | 2 × average daily budget | 200 |
| In one month | 30.4 × average daily budget | 3,040 |
Want to spend a set amount in a month? Set the daily budget to that amount divided by 30.4. 3,000 a month is 98.68 a day.
Why Google spends more on some days
Traffic goes up and down from day to day. Google spends more on days when it expects more clicks and conversions and less on quiet days, so the month averages out to your daily budget. Google calls the high days overdelivery. Its own example: at 10 a day, a campaign might spend 15 on one day and 8 on another, but never more than 20 in a day or 304 in the month (Google Ads: Budgets overview).
30.4 is the average number of days in a month (365 ÷ 12). In the month a campaign starts, Google counts only the days it was running (Google Ads: About spending limits).
The June 2026 change: ad schedules no longer cut the month
Since 1 June 2026, if an ad schedule turns a campaign off on some days of the week, Google still paces it to spend 30.4 times the daily budget in the month. It just packs that spend into the days the campaign runs (Google Ads: Changes to budget pacing for Ad Scheduling).
| Campaign | Before June 2026 | Now |
|---|---|---|
| 100 a day, scheduled to run 20 days in the month | Paced to 2,000 | Paces to 3,040 |
That is 52% more for the same settings. Schedules that only switch off some hours of the day are not affected. The fix is the same rule as above: divide what you want to spend in the month by 30.4, not by the days the campaign runs. For 2,000 over those 20 days, set 65.79 a day. On days it runs it can still spend up to twice that.
Changing the budget halfway through the month
When you change the daily budget, Google says spend for the rest of the month won't go over the new daily budget times the calendar days left (About spending limits). So on the 21st of a 30-day month, a new budget of 100 a day allows up to 1,000 more, as 10 days are left including the 21st. The daily limit moves with it: 2 times the highest daily budget you set that day.
Charged more than the limit? Check served vs billed cost
Sometimes the clicks you received cost more than your limit. Google calls that served cost. What you pay is billed cost, and Google says it never goes over the daily or monthly spending limit; Google covers the difference (Google Ads: About overdelivery).
- In Google Ads, open Campaigns, then Insights and reports, then Report editor.
- In the Billing section of the template gallery, open the Billed cost report.
- Served cost minus billed cost is the overdelivery Google did not charge you for.
How to cap spend
- Daily budget = monthly amount ÷ 30.4. Keeps the month on your number. Single days can still reach 2 times the daily budget.
- Campaign total budget. One budget for fixed dates. Google says there is no daily limit and you are never charged more than the total. It can only be chosen when a new campaign is set up, the budget type can't be changed later, and it runs 3 to 90 days, or up to a year for Demand Gen and YouTube (Google Ads: About campaign total budgets).
- Shared budget. One daily amount split across several campaigns, so a quiet campaign's leftover goes to a busy one. Not for campaigns in a campaign group or an experiment (Google Ads: Choose your bid and budget).
Meta works differently
Meta says it may spend up to 75% over your daily budget on a day, but no more than7 times the daily budget in a week from Sunday to Saturday (Meta: About daily budgets). So check Meta by the week, and Google by the month.
The costly Meta mistake is a budget type switched by accident. A 3,000 lifetime budget for a 30-day campaign spreads 3,000 over the dates. Switched to a 3,000 daily budget, the same campaign may spend up to 21,000 in a single week.
Five set-up mistakes that cause real overspend
The platform rules above are expected. These are the mistakes that turn into five-figure bills:
- A monthly budget typed as the daily budget. 3,000 meant for the month, entered as 3,000 a day, allows up to 91,200 in the month.
- Lifetime switched to daily on Meta. The whole flight's budget, every day.
- A decimal or comma slip. 50.00 typed as 5000 is 100 times the budget. Compare each budget with the others in the account.
- Counting on an ad schedule to cut spend. Since June 2026 Google paces to the full month anyway.
- No end date. A daily budget keeps going until someone stops it, through weekends and holidays.
Each of these can be seen in the campaign settings before launch. A second pair of eyes on the budget, the budget type and the dates catches most of them.
Plan the budget before launch
The free budget pacing calculator works out the daily budget for each campaign from its total and dates, and shows whether a running campaign is on track. Paste a Meta Ads Manager or Google Ads export and the rows fill in. It runs in your browser, so nothing you paste is sent to us. To see what ROAS the budget has to earn, try the ROAS and break-even calculator.