Customer acquisition cost formula
Two CAC views. Two different cost boundaries.
Marketing spend ÷ new customers Use the marketing boundary you deliberately selected: advertising-only, fully loaded marketing, or a documented custom boundary.
(Marketing spend + sales spend) ÷ new customers Adds the governed sales cost boundary to the same-period marketing costs before dividing by acquired customers.
The formula is simple. The hard part is keeping cost inclusions and the customer event consistent enough for the ratio to mean the same thing next month.
The useful question is not only “What is our CAC?” It is “Which costs are inside this CAC, which customers are in the denominator, and is that definition stable between periods?”
What counts as marketing spend?
You choose the boundary, but you must name it. An advertising-only view includes paid media and directly attributable advertising costs. That can be useful for media optimization, but it should be labeled advertising-only CAC rather than presented as the company’s complete marketing CAC.
For a more complete operating view, marketing spend will usually include:
- advertising and paid media;
- salaries, benefits, and other employment costs for marketing staff;
- agencies, freelancers, consultants, and other marketing services;
- software and tools, including platforms such as Adobe and Ahrefs;
- creative production, research, events, sponsorships, and other demand-generation costs when they are part of the chosen boundary.
Shared costs do not need a perfect allocation to be useful, but the allocation rule must be documented and applied consistently. A custom boundary is valid when the inclusions and exclusions remain visible.
What counts as sales spend?
Sales spend covers the costs of converting demand into customers after or alongside marketing. Depending on the operating model, that can include sales salaries, benefits, commissions, sales leadership, outsourced sales development, sales enablement, travel, and the sales-controlled share of CRM or prospecting software.
Do not silently place sales costs inside “marketing spend.” Keep the two inputs separate, then add them only for the marketing + sales CAC view. If a person, agency, or system supports both functions, choose a reasonable allocation rule and disclose it.
Worked example
If marketing spend is $75,000, sales spend is $30,000, and 140 new customers are acquired in the same period:
- Marketing-only CAC = $75,000 ÷ 140 = $535.71
- Fully loaded CAC = ($75,000 + $30,000) ÷ 140 = $750.00
- The cost-boundary difference is $214.29 per customer
Method and assumptions
Use costs and customers from the same time window. Decide whether “new customer” means signed, activated, paid, or another governed event. Keep refunds, reactivations, expansion revenue, staff costs, agency fees, software, creative production, and sales compensation either consistently included or consistently excluded.
Limits
CAC is an average, not a causal channel estimate. It does not show payback timing, gross margin, customer quality, cohort retention, or what would happen if spend changed. Compare periods only when the cost boundary and customer definition are the same.
Continue into lifecycle operations to define the customer event and preserve the acquisition-to-revenue handoff.