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Google Ads Budget Calculator

Google Ads budgets follow published rules most calculators ignore: monthly spend is capped at 30.4 times your daily budget (365 days ÷ 12), any single day may charge up to twice the daily budget through overdelivery, and Google recommends around 30 conversions per month before Smart Bidding results mean anything. This calculator applies all three. From a daily budget and your average CPC it projects the monthly ceiling, the worst single-day charge, clicks per month — and, once you add a conversion rate, leads, sales, cost per lead and cost per sale, with an explicit flag for whether the account clears the Smart Bidding data floor. The funnel reading turns a budget from a number you type into a business case you can defend.

Your actual average, from the campaign's 'Avg. CPC' column.

Conversion rate. Leave blank to model traffic only.

Your close rate on leads. Blank = no sales row.

Monthly spend ceiling

$608.00

$20.00/day × 30.4 — Google's official monthly cap, however much any single day overdelivers.

Worst single-day charge
$40.00

Google may spend up to 2× your daily budget on one day and compensate on quieter days. A charge above this line is a billing error worth disputing.

Clicks per month
243

8 per day at $2.50 average CPC.

Leads per month
12.2

At a 5% conversion rate — $50.00 per lead.

Sales per month
3

At a 25% close rate — $200.00 per sale.

Smart Bidding readiness
Below Google's floor

Google recommends ~30 conversions per month (50 for Target ROAS) before Smart Bidding performance means anything. Raise the budget, widen targeting, or raise conversion rate — or expect noisy automated bidding.

Based on Google's published rules: monthly spend is capped at 30.4× the daily budget, single days may charge up to 2× the daily budget, and Google recommends ~30 conversions per month (50 for Target ROAS) before Smart Bidding results are meaningful. Actual CPCs vary by auction — model with your account's real averages.

How to use Google Ads Budget Calculator

  1. 1

    Enter daily budget and average CPC

    Use your account's actual average CPC from the 'Avg. CPC' column once it has history; before that, Keyword Planner's estimates read as a range.

  2. 2

    Add the funnel rates

    Conversion rate on clicks gives leads and cost per lead; close rate on leads gives sales and cost per sale. Leave blank to model traffic only.

  3. 3

    Check the Smart Bidding flag

    Below Google's ~30-conversions-per-month floor, automated bidding optimizes noise — consolidate campaigns, count deeper conversions, or raise volume before trusting tCPA.

Why use this tool

  • Monthly ceiling from Google's official 30.4× rule
  • Single-day overdelivery warning: the 2× charge explained
  • Clicks, leads and sales projected down the funnel
  • Cost per lead and cost per sale from your real rates
  • Smart Bidding readiness flag against Google's 30-conversion floor
  • Free and private — budget details never leave the browser

Frequently asked questions

How is the Google Ads monthly budget calculated?
Google caps monthly spend at 30.4 times your average daily budget — 365 days divided by 12. A $20/day budget is a $608 monthly commitment. Some days spend less; the cap is what you will never exceed.
Why was I charged more than my daily budget?
Overdelivery: on high-demand days Google may spend up to 2× your daily budget, then compensate on quieter days so the month stays within 30.4×. A charge above twice your daily budget on any single day is a genuine billing error worth disputing.
How many clicks will my budget buy?
Monthly budget divided by average CPC: $608 at a $2.50 CPC is about 243 clicks a month, or 8 a day. Use your account's real average CPC — Keyword Planner estimates drift high, and planning on them is how budgets silently under-deliver.
What is the Smart Bidding conversion floor?
Google recommends judging Smart Bidding over periods with at least 30 conversions (50 for Target ROAS). Below that volume, automated bidding optimizes noise — targets swing and 'learning' never ends. The flag in this calculator tells you which side of the floor your budget lands on.
How do I work out cost per lead from my budget?
Cost per lead is CPC divided by conversion rate: a $2.50 CPC at a 5% conversion rate is $50 per lead. Add your close rate and the same chain gives cost per sale — the number that decides whether the budget is a business or a hobby.
Should I split one budget across several campaigns?
Only when audiences genuinely need different messages. Every split divides your monthly conversions, and conversions are the data automated bidding learns from — three campaigns at 10 conversions each are all below the floor that one at 30 clears. Consolidation is the cheapest budget increase available.

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