The short answer

Customer acquisition cost, or CAC, is the total sales and marketing cost for a period divided by the number of new customers acquired in that period.

Then compare CAC with the contribution those customers generate, when they generate it, and how many stay or buy again. Revenue alone can make unprofitable marketing look successful.

Calculate blended CAC

Include ad spend, agency or freelancer cost, marketing software, sales commissions, event fees, creative production, and the fair value of labor devoted to acquisition.

Suppose one month includes:

• $600 ads.
• $250 contractor design.
• $100 marketing software allocation.
• 15 owner hours valued at $30, or $450.

Total acquisition cost is $1,400. If you gained 14 new paying customers, blended CAC is $1,400 ÷ 14 = $100.

Do not divide by leads, subscribers, or orders from existing customers.

Compare CAC with contribution

A new customer pays $240. Product, fulfillment, payment, and support costs tied to that sale total $90. First-sale contribution is $240 − $90 = $150.

With $100 CAC, $50 remains from the first sale before fixed overhead. If refunds average $20 per acquired customer, only $30 remains. That may be acceptable or dangerously thin depending on the business.

Add time and repeat purchases

If customers reliably buy again, calculate contribution over a defined window, such as 90 days or 12 months. Use observed retention, not a hopeful lifetime estimate.

Also check payback. Spending $10,000 to earn contribution over two years can strain a small business even if the eventual total is positive.

Use channel CAC carefully

For one channel, divide that channel’s attributable cost by new customers reasonably attributed to it. Keep an “unknown” source rather than forcing every customer into the last link clicked.

Compare customer quality too. A referral channel with $140 CAC may beat ads at $90 if referred customers buy more, stay longer, and need fewer refunds.

The SBA’s planning guidance connects marketing strategy, financial projections, costs, and revenue. Your CAC sheet is the monthly bridge between those pieces.

Sources and further reading

• SBA: Plan Your Business

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Helpful WAHMN tool

If you want a guided tool for this, the Monthly Profit Tracker can help you compare customer-acquisition cost with the revenue and profit those customers produce.

Related Questions

• How do I set a realistic marketing budget for a small business?
• How early should I start marketing before my business officially launches?
• When should I keep marketing in-house, and when is it worth hiring help?
• Why isn't my marketing generating sales, and how do I diagnose what is failing?

Related WAHMN resource

If you want a complete system for planning, creating, distributing, and measuring useful content, this course carries the process further. See Content Marketing Business.