What is CAC (Customer Acquisition Cost)?
CAC is the total cost of acquiring a new customer. It tells you what it costs to buy growth, and it is the foundational metric behind payback periods and LTV:CAC ratios.
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Definition
CAC (Customer Acquisition Cost) is the total cost of acquiring a new customer — all the sales and marketing spend it took, divided by the number of new customers won in the same period. It's the foundational unit-economics metric: it tells you what it costs to buy growth, and it's the input behind CAC payback and the LTV:CAC ratio.
How to calculate CAC.
Divide total sales and marketing spend by new customers acquired in the same period:
CAC =
Total Sales & Marketing Spend ÷ New Customers Acquired
SaaS teams track two variations of this calculation:
A thorough CAC includes ad spend, sales and marketing salaries, agency fees, tool costs, and overhead. A simpler working version is channel ad spend divided by new customers acquired from that channel. Whichever definition you use, always count paying customers, not trial signups.
CAC example.
SaaS channel metrics over a 30-day period:
The blended $300 CAC hides real variance: Google brand search acquires at $141, while Meta prospecting sits at $233. Only per-channel CAC tells you where to invest next.
Why CAC matters for attribution.
CAC is only actionable when it's measured per channel and against real paying customers. Blended CAC averages your efficient and wasteful channels into one number that hides the decision that matters. And if you count trial signups instead of paying customers, CAC looks artificially low — until those trials don't convert.
That's an attribution problem at heart: you need to tie each dollar of spend to the Stripe conversion it produced. Signal Sparrow computes true CAC per channel from reconciled revenue attribution, then pairs it with CAC payback and true ROAS — so CAC becomes a budgeting input you can trust, not a blended average you have to caveat.
Questions, answered.
Everything teams ask before switching their attribution to Stripe truth. Still curious? Talk to us.
CAC (Customer Acquisition Cost) is the total sales and marketing cost to acquire a new customer, calculated by dividing acquisition spend by the number of new customers won in the same period.
Divide total sales and marketing spend by new customers acquired. Blended CAC uses all spend and all customers; paid CAC uses paid spend and paid-acquired customers. Count paying customers, not trials.
Blended CAC includes all acquisition (paid and organic) and all new customers; paid CAC isolates paid channels. Paid CAC shows ad efficiency; blended CAC shows overall acquisition cost.
A full CAC includes ad spend plus sales and marketing salaries and commissions, tools, agency fees and content costs. A simpler working version uses ad spend divided by new customers per channel.
There's no universal number — CAC is only meaningful relative to what a customer is worth. Judge it through CAC payback (how fast you recover it) and the LTV:CAC ratio rather than as an absolute figure.
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