The Complete Guide to CAC and CAC Payback
By Arshi Khan, Founder of Just4Marketing · Last reviewed October 2026
Customer acquisition cost tells you what it costs to win a customer; CAC payback tells you how long that customer takes to earn it back. Together with lifetime value, they show whether growth is creating value or burning cash. This guide covers each formula and the benchmarks B2B companies are measured against.
The three formulas
CAC = sales & marketing spend ÷ new customers. Payback (months) = CAC ÷ (ARPA × gross margin). LTV = ARPA × gross margin ÷ monthly churn rate, which estimates the gross profit a customer brings in over their expected lifetime.
How churn changes lifetime value
| $200/month at 80% margin | Average lifetime | LTV | LTV : CAC ($1,500) |
|---|---|---|---|
| 1% monthly churn | 100 months | $16,000 | 10.7 : 1 |
| 2% monthly churn | 50 months | $8,000 | 5.3 : 1 |
| 3% monthly churn | 33 months | $5,333 | 3.6 : 1 |
| 5% monthly churn | 20 months | $3,200 | 2.1 : 1 |
Improving unit economics
Raise revenue per account
Pricing and packaging changes shorten payback faster than most marketing optimizations.
Cut churn
Halving churn doubles lifetime value with no change in acquisition cost.
Measure CAC by channel
A blended CAC can hide one expensive channel. Calculate it separately for paid ads, outbound sales, and referrals.
Frequently asked questions
How do you calculate CAC?
CAC = total sales and marketing spend in a period ÷ new customers won in that period. Include salaries, commissions, ad spend, tools, and agency fees for sales and marketing. With $60,000 spent and 40 new customers, CAC is $1,500.
How is CAC payback period calculated?
CAC payback = CAC ÷ (average monthly revenue per account × gross margin). It uses gross profit rather than revenue because the cost of serving the customer has to be covered first. A $1,500 CAC with $200 a month at 80% margin pays back in about 9.4 months.
What is a good CAC payback period?
Many B2B SaaS companies aim for 12 months or less for small and mid-sized customers, and up to 18–24 months for enterprise customers who stay longer. Shorter payback means growth needs less outside funding.
What is a good LTV to CAC ratio?
A common benchmark is 3:1 — a customer generates three times their acquisition cost in gross profit over their lifetime. Well below 3:1 suggests acquisition is too expensive; far above 5:1 can mean you're underinvesting in growth.