Customer Acquisition Cost (CAC) Calculator
Calculate blended CAC, payback period, and the rough LTV : CAC ratio.
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Customer Acquisition Cost (CAC) is the average sales and marketing spend required to acquire one new paying customer. It's the single most important number in growth — paired with LTV, it tells you whether to step on the gas or hit the brakes.
CAC = (Marketing spend + Sales spend) ÷ New customers
CAC payback (months) = CAC ÷ Monthly gross profit per customer
Teams that don't measure CAC always think their marketing is "working" because revenue grew. Then a paid channel softens and the unit economics collapse. CAC turns "we got a deal" into "we got a deal that pays back in 7 months at a 4× LTV ratio."
Worked examples
$35k blended quarterly spend, 80 new customers, $1,200 ARPU, 80% gross margin. CAC = $438, payback ≈ 5.5 months.
$250k spend, 25 customers, $24k ACV, 75% gross margin. CAC = $10k, payback ≈ 6.7 months.
- Counting only ad spend — sales salaries, BDR tooling, and content all belong in CAC.
- Attributing all customers to paid when organic and referral did the work (use blended CAC).
- Comparing CAC across very different segments (SMB vs enterprise need separate models).
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