How Google Ads daily budgets work, and why you spent more than your budget

It's the average you're comfortable spending each day over a month. Google spends more on days when you're more likely to get clicks and conversions, and less on others.

• 30.4 is the average number of days in a month. To turn a monthly budget into a daily one, divide by 30.4.
• These limits apply to most campaigns, according to Google.

Sources: Google Ads Help: About average daily budgets, checked 15 October 2026; Google Ads Help: Set and change an average daily budget for your campaign, checked 15 October 2026

You can change it as often as you like.

1. In Google Ads, open the Campaigns menu and select Campaigns.
2. Find the campaign you want to edit.
3. In the Budget column, select the pencil icon.
4. Enter a new average daily budget.
5. Select Save.

Source: Google Ads Help: Set and change an average daily budget for your campaign, checked 15 October 2026

The change applies straight away and affects both limits. On the day you change it, the daily limit is based on the highest budget you set that day. For the rest of the month, spend is capped at what you've already spent plus the new daily budget times the days left.

• Google's example: with $270 spent and 5 days left, raising the budget from $10 to $50 makes the monthly limit $270 + ($50 x 5) = $520, and that day's limit $100.
• Lowering it to $5 in the same position gives a monthly limit of $270 + ($5 x 5) = $295. The day of the change keeps its $20 limit.
• Changing a campaign's end date also counts as a budget change.

Source: Google Ads Help: How budget changes take effect, checked 15 October 2026

Yes, for a short promotion. A campaign total budget is a fixed amount for 3 to 90 days, available for Search, Shopping and Performance Max campaigns.

• There's no daily cap, so spend varies by day, but the total is never exceeded.
• If you change the total or end date, Google re-paces the remaining budget over the remaining days.
• You can't switch an existing campaign from a daily to a total budget; you need a new campaign.

Source: Google Ads Help: How budget changes take effect, checked 15 October 2026

Overdelivery is when the cost of the clicks or impressions you received goes over your spending limits. Google says you never pay more than those limits.

1. In Google Ads, open the Campaigns menu.
2. Open Insights and reports and select Report editor.
3. In the Billing section of the Template gallery, choose the Billed cost report.
4. For each campaign, subtract Billed cost from Served cost. Download the report as a .csv file to do this in bulk.

Source: Google Ads Help: About overdelivery and your average daily budget, checked 15 October 2026

Check these:

• Limited by budget: your campaign regularly hits its budget and could get more clicks and impressions. Google shows a recommended budget for these campaigns.
• Spend was double one day: that's within the daily limit of 2 times your budget.
• Spend was low on some days: Google spends less when clicks or conversions are less likely, and makes up for it on busier days.
• Leftover budget: Google suggests checking regularly for campaigns with unspent budget as well as limited ones.

Sources: Google Ads Help: Set and change an average daily budget for your campaign, checked 15 October 2026; Google Ads Help: About average daily budgets, checked 15 October 2026

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