What is CAC payback period?
CAC payback period is how many months of gross profit from a customer it takes to recover what you spent to acquire them. SaaS investors and operators use it to judge whether growth is cash-efficient.
CAC payback (months) = CAC ÷ Monthly gross profit per customer
Monthly gross profit = Monthly revenue per customer × Gross margin %
With $300 CAC, $50 monthly revenue per customer, and 80% margin → monthly gross profit = $40 → payback = 300 ÷ 40 = 7.5 months.
How to calculate CAC payback (step by step)
- Determine fully-loaded CAC — all sales and marketing costs ÷ new customers. Use the CAC calculator if you need to build this number.
- Calculate monthly gross profit per customer — monthly revenue per customer × gross margin %. For SaaS, this is MRR × margin; for ecommerce, average monthly spend × margin.
- Divide CAC by monthly gross profit — the result is payback in months.
Worked example: two SaaS companies compared
Two companies with the same $300 CAC but different pricing models:
| Metric | Company A (SMB SaaS) | Company B (Enterprise SaaS) |
|---|---|---|
| Monthly revenue per customer | $50 | $500 |
| Gross margin | 80% | 85% |
| Monthly gross profit | $40 | $425 |
| CAC | $300 | $3,000 |
| Payback period | 7.5 months | 7.1 months |
| LTV (36-month life) | $1,440 | $15,300 |
| LTV:CAC ratio | 4.8:1 | 5.1:1 |
Both have similar payback (~7 months) and healthy LTV:CAC ratios — despite Company B having 10× the CAC and 10× the monthly revenue. Payback normalizes across pricing tiers; it's the speed of capital recovery that matters, not the absolute CAC.
Payback progress month by month
For Company A ($300 CAC, $40 monthly gross profit):
| Month | Cumulative gross profit | CAC recovered? |
|---|---|---|
| 1 | $40 | No — $260 remaining |
| 3 | $120 | No — $180 remaining |
| 5 | $200 | No — $100 remaining |
| 7 | $280 | Almost — $20 remaining |
| 7.5 | $300 | Fully recovered |
| 8 | $320 | +$20 profit from this customer |
| 12 | $480 | +$180 profit in year 1 |
Every month after 7.5, this customer's gross profit is pure contribution. If the customer churns before 7.5 months, the company loses money on that acquisition — which is why payback period and retention are complementary metrics.
Why it matters more than LTV:CAC alone
LTV:CAC ratio tells you if a customer is worth more than they cost over their lifetime — but not when you get your money back. A 5:1 LTV:CAC with 24-month payback can still kill cash flow if you're scaling paid acquisition. Payback connects CAC to monthly unit economics and cash runway.
What's a good CAC payback?
For B2B SaaS, 12 months or less is a widely cited benchmark; 6 months is strong. Ecommerce and subscription boxes often target shorter payback (1–3 months) because margins and retention differ. Compare payback to your cash runway and to how long customers actually stay — use the customer lifetime value calculator for the other side of the equation.
How to shorten payback
Raise price or ARPU, improve gross margin, lower CAC through better conversion rates, or increase early-month revenue with annual prepay discounts. Annual plans paid upfront can dramatically improve cash payback even when monthly metrics look similar — a $600 annual payment on a $300 CAC means payback is instant (0 months) rather than 7.5.