The right budget depends on CPC, industry, and conversion rate — not gut feel. Here’s how to calculate a realistic minimum.
Why Small Budgets Fail
Budgets under $500/month rarely work in paid search. Not because Google penalizes small spenders, but because you need enough data to optimize. At a $5 CPC and $1,000/month budget you get 200 clicks. At a 3% conversion rate that’s 6 conversions — not enough for Smart Bidding, not enough for Quality Score trends, not enough to separate signal from noise. Under-funded accounts stay in ‘learning’ forever.
The Minimum Budget Math
To run a working Google Ads campaign, you need: (CPC × clicks-per-conversion × 30 conversions/month) at minimum. Example: $4 CPC × 33 clicks per conversion (3% CR) × 30 conversions = $3,960/month minimum to be in learning-optimal range. If your numbers show under $1,500/month, pick a tighter niche or tighter geo — don’t run a half-starved campaign.
Realistic Ranges by Industry
Typical healthy paid search budgets by sector: local services (plumber, lawyer) $1,500–$5,000/month, SMB B2B (SaaS, agencies) $3,000–$10,000, ecommerce $2,000–$50,000+ depending on volume, legal and finance where CPCs hit $30+ often need $10,000 minimum. These are monthly floors for the campaign to work at all — not aspiration numbers.
Allocating Budget Across Campaigns
Concentrate 70–80% of budget on your two highest-intent, proven-converting campaigns. Spread the remaining 20–30% across testing: new keywords, new audiences, competitor terms. Too-thin-across-too-many campaigns is how new accounts die: every campaign hits the $30–50/day minimum Smart Bidding needs, and nothing has enough data to optimize.
Daily Budget vs Monthly
Google uses daily budget × 30.4 as the monthly cap. Your daily spend can vary — up to 2x your daily budget on high-demand days — but won’t exceed the monthly total. Don’t obsess over individual daily overspend if monthly stays on target. Watch for campaigns consistently hitting budget every day: either the campaign is working and budget is throttling it, or your bids are too high and you’re not bidding efficiently.
When to Scale Budget
Scale when: CPA is at or below target for 4+ weeks, impression share lost to budget is >20%, and your conversion volume is 50+/month per campaign. Scale 20–30% per week, not 2x overnight — Smart Bidding needs time to relearn at new volume. Scaling before these signals shows up just spends more at a worse CPA. Patience here pays better than aggressive scaling.
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