"How much should I spend on ads?" is one of the most common questions we get — and the worst answer is a flat number with no context. The right advertising budget depends on your revenue, your industry, your goals, and what a new customer is worth to your business.
Here's the framework that actually helps small businesses set budgets that work.
Start With What a Customer Is Worth to You
This is the only number that matters for setting an ad budget: your customer lifetime value (CLV). How much revenue does a single new customer generate over their relationship with your business?
For a restaurant, a new regular customer might visit 30 times per year at $35 per visit — $1,050/year. For an HVAC contractor, a new customer might represent a service call ($200) plus a maintenance contract ($400/year) plus eventual equipment replacement ($6,000) — potentially $8,000+ over 10 years.
Once you know what a customer is worth, you can work backward from a target cost-per-acquisition to set a sensible budget.
The Percentage of Revenue Framework
Industry benchmarks for marketing spend as a percentage of revenue:
- Retail and e-commerce: 8–15% of revenue
- Restaurants: 3–9% of revenue
- Service businesses (HVAC, plumbing, legal, etc.): 5–12% of revenue
- B2B professional services: 6–10% of revenue
- Real estate: 10–15% of revenue (highly variable)
These are total marketing budgets, not just digital advertising. Allocate based on which channels produce results for your specific business.
The Minimum Viable Budget
For Google Ads specifically, there's a practical minimum below which campaigns can't generate enough data to optimize:
- Low-competition local markets (Shallotte, Brunswick County small categories): $300–$600/month can work
- Moderate competition (general service businesses in Myrtle Beach, Wilmington): $600–$1,500/month
- High competition (legal, real estate, medical in larger markets): $1,500–$5,000+/month
Below these thresholds, campaigns often run out of budget before generating enough clicks to learn and optimize. You get inconclusive data and conclude "ads don't work" — when the reality is the budget was too small to test properly.
The Math That Should Drive Your Budget Decision
Work backwards from your economics:
- What is a new customer worth? — let's say $1,500
- What's your website's conversion rate? — let's say 5% (5 of 100 visitors become leads)
- What percentage of leads become customers? — let's say 30%
- So 100 clicks → 5 leads → 1.5 customers → $2,250 in revenue
- What can you afford to pay for 100 clicks? — if a reasonable profit margin allows for a 20% customer acquisition cost, you can spend up to $300 to acquire a $1,500 customer → $300/100 clicks = $3 max CPC
If the actual CPC for your keywords is $8, those economics don't work at that conversion rate. You either need to improve your website's conversion rate, find cheaper keywords, or accept a lower margin on acquired customers.
Scaling: When to Spend More
The right signal to increase ad spend is positive ROI at the current level. If you're spending $1,000/month and generating $3,000 in trackable revenue from ads — increase the budget. You're buying dollars for cents.
The mistake many small businesses make is setting an ad budget based on what they're comfortable spending rather than what the data supports. If the ROI is there, constraining budget out of caution is leaving money on the table.
What to Track to Know If It's Working
Spending without measurement is just gambling. The metrics that matter:
- Cost per click (CPC) — how much each visitor costs
- Conversion rate — what percentage of visitors take the desired action (call, form fill, booking)
- Cost per lead (CPL) — total spend ÷ number of leads generated
- Cost per acquisition (CPA) — total spend ÷ number of new customers closed
- Return on ad spend (ROAS) — revenue attributable to ads ÷ ad spend
Without conversion tracking set up in Google Ads and Google Analytics, you're flying blind. This is the single most important thing to get right before spending significant budget.
