Google Ads Budget Calculator for Small Business
Plan a starter Google Ads budget: the 30.4 monthly rule, the 2× single-day surprise on your invoice, and what $15/day actually buys. Free.
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
$456.00
$15.00/day × 30.4 — Google's official monthly cap, however much any single day overdelivers.
- Worst single-day charge
- $30.00
- Clicks per month
- 228
- Leads per month
- 9.1
- Smart Bidding readiness
- Below Google's floor
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.
7.5 per day at $2.00 average CPC.
At a 4% conversion rate — $50.00 per lead.
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.
Starting values are set for a typical small business scenario — change any field to match yours. Need the plain version? Google Ads Budget Calculator.
About this scenario
The two budget surprises that hit small advertisers are both rule-based, not random. First: Google bills up to 30.4 times your daily budget per month — a $15/day budget is a $456/month commitment, not $450, and not $15 × the days you happened to run. Second: on any single day Google may spend up to twice your daily budget (overdelivery), compensating on quieter days — which reads as an error on the invoice the first time you see a $30 day.
Model a starter budget below — $15/day at a $2.00 CPC buys about 228 clicks a month — then read what that budget can and cannot expect, and when to raise spend versus improve the funnel.
What $15/day actually buys
| Figure | Value | Where it comes from |
|---|---|---|
| Monthly ceiling | $456 | $15 × 30.4 — Google's published monthly multiplier |
| Worst single day | $30 | 2× overdelivery on a high-demand day |
| Clicks | ≈228/month | $456 ÷ $2.00 CPC |
| Leads at 4% | ≈9/month | $50 per lead |
The two beginner budget mistakes
- Judging the account after 20 clicks. At 9 leads a month, every metric is noise; commit to 4-8 weeks or a fixed click volume before changing anything but obvious broken settings.
- Splitting $15/day across four campaigns. Budget fragmentation starves every campaign; one campaign learning from 228 clicks beats four campaigns learning from 57 each.
When to raise budget vs improve conversion rate
At small scales the conversion-rate lever usually dominates, because CPC is largely set by the auction while your conversion rate is set by your own page. The arithmetic: halving the budget and doubling the conversion rate produces the same leads for half the spend — and the page change is free. The table that decides it:
| Approach | Spend | Leads | Cost per lead |
|---|---|---|---|
| Double the budget | $912/month | ≈18 | $50 |
| Halve budget, double conversion rate | $228/month | ≈9 | $25 |
Frequently asked questions
How much should a small business spend on Google Ads?
Enough to buy meaningful data: at a $2-4 CPC, $300-600 a month buys 75-300 clicks, which is enough to judge a landing page and find the obvious negatives — and still below the volume where Google's automated bidding performs well. Start where you can sustain 2-3 months without flinching, because learning is front-loaded.
Why was I charged more than my daily budget?
Overdelivery: Google may spend up to 2× your daily budget on a single day when demand spikes, then compensate on quieter days. The monthly total never exceeds 30.4× the daily budget. A single day above 2× is a genuine billing error worth disputing.
Is the monthly budget daily × 30 or × 30.4?
30.4 — Google's official multiplier (365 days ÷ 12). A $15 daily budget is a $456 monthly commitment. Calculators and rules of thumb using ×30 quietly understate the ceiling by about 1.3%.
How long before I know if Google Ads works for me?
Give it 4-8 weeks or roughly 100-300 clicks per campaign, whichever comes first. Below that volume, conversion-rate swings are statistical noise. Judge trends, not days — and change one thing at a time so you know what moved.
Should I use Google's automated bidding on a small budget?
Start manual or 'Maximize clicks' with a CPC cap until the campaign reliably produces conversions. Google's own guidance suggests judging Smart Bidding over periods with at least 30 conversions — a threshold most starter budgets reach only after months, if at all. Automated bidding on 3 conversions a month optimizes noise.
What CPC should I plan with?
Your own actual average CPC once the account has history; before that, Keyword Planner's top-of-page bid estimates for your keywords, read as a range. Planning with the low end of a CPC estimate is how budgets silently deliver half the expected clicks.