What Is the CAC Payback Period?
The CAC Payback Period measures how many months it takes for a customer's gross margin contribution to repay their acquisition cost. It indicates how quickly your growth investment recycles into cash that can fund more growth.
Formula
CAC Payback Period = CAC / (ARPU × Gross Margin %)
Where ARPU is Average Revenue Per User per month.
For a company with $600 CAC, $100/mo ARPU, and 80% gross margin:
Payback Period = $600 / ($100 × 0.80) = 7.5 months
Benchmarks
| Payback Period | Assessment |
|---|---|
| < 6 months | Excellent — fast cash recycling |
| 6 – 12 months | Good — standard for healthy SaaS |
| 12 – 18 months | Acceptable for enterprise SaaS |
| > 18 months | Concerning — capital-intensive growth |
Why Payback Period Matters More Than LTV:CAC
LTV:CAC tells you the total return but ignores timing. A 5:1 LTV:CAC with a 24-month payback requires significant capital to fund growth, while a 3:1 ratio with a 4-month payback lets you reinvest rapidly.
Cash-efficient companies focus on payback period because it determines growth velocity — how fast you can redeploy capital.
Adjusting for Payment Terms
Annual prepaid plans dramatically improve payback:
| Pricing | Monthly Revenue | Payback on $600 CAC |
|---|---|---|
| Monthly ($100/mo) | $80 GM/mo | 7.5 months |
| Annual prepaid ($960/yr) | $960 upfront, $768 GM | Immediate |
CAC Payback Period in AI-Run Companies
AI-run companies typically achieve shorter payback periods through two mechanisms: lower CAC (AI handles marketing and sales) and higher gross margins (AI handles support at lower cost). A payback period under 3 months is common for well-optimized AI-run businesses.
On EvolC, short payback periods signal that an AI company can scale aggressively without burning cash — a critical factor for investors evaluating capital efficiency.