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CAC Formula: How to Calculate Customer Acquisition Cost

The Customer Acquisition Cost (CAC) formula quantifies the total expenditure required to acquire a new customer, serving as a vital metric for evaluating the efficiency of sales and marketing efforts.

3 variables. Published Mar 12, 2026. Updated Mar 27, 2026. By AI Biz Hub.

Formula
CAC = Sales And Marketing Spend / New Customers

Variables

CAC

CAC

The average cost to acquire one new paying customer, in currency units. Compare it against customer lifetime value and payback period to judge whether a channel is sustainable.

SMS

Sales And Marketing Spend

Total sales and marketing spend for the period in currency units: ad budget, salaries, tooling, and commissions attributable to acquisition. The numerator.

NC

New Customers

The count of new paying customers won in the same period. Use only genuinely new customers, not renewals or expansions.

Step by step

  1. 1

    Set the baseline case with the real calculator inputs.

    Sales Marketing Spend = $32,000, New Customers = 40, Monthly ARPU = 129, Gross Margin Percent = 78.0%

  2. 2

    Add up every sales and marketing cost for the window (ad spend, salaries, tools, agency fees) so the numerator is complete.

    Ads 20,000 plus salaries 10,000 plus tools 2,000 gives 32,000 total spend.

  3. 3

    Apply the formula and read the first calculator outputs, not just the headline assumption.

    The calculator lands with customer acquisition cost at $800 and payback period at 7.95.

  4. 4

    Re-run per channel rather than blended, since a healthy average can hide one channel acquiring customers far above its payback ceiling.

    Blended CAC of 800 may split into 400 for organic and 1,500 for paid search.

Worked example

CAC sample case

Sales Marketing Spend

$32,000

New Customers

40

Monthly ARPU

129

Gross Margin Percent

78.0%

CAC = Sales And Marketing Spend / New Customers using sales marketing spend $32,000, new customers 40, monthly ARPU 129, gross margin percent 78.0%.

The calculator lands with customer acquisition cost at $800 and payback period at 7.95.

Common variations

Scenario variants are useful because fixed assumptions rarely survive contact with real life unchanged.
Use CAC Calculator to compare the baseline result with one stressed case before relying on a single answer.

Run the numbers next

Sources

  1. Customer Acquisition Cost (CAC) , Investopedia
  2. Customer Acquisition Cost: Definition and FAQs , HubSpot Blog

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