How CAC payback is actually calculated
The formula most marketers use is wrong. The right one:
CAC payback (months) = CAC / (MRR × Gross Margin)
The gross margin part is what most people skip. If your CAC is $500 and your MRR is $99, the naive math says payback in 5 months. But if your gross margin is 80%, you only actually keep $79 per month. Real payback is 6.3 months.
For SaaS specifically, gross margin includes hosting, support staff, customer success, and third-party API costs. Most B2B SaaS gross margins land at 70-85%.
What good CAC payback looks like
- Under 12 months: Best-in-class. You can grow aggressively because new customer dollars compound fast.
- 12-18 months: Healthy. What most VCs want to see for Series A/B SaaS. The Bessemer benchmark.
- 18-24 months: Watch zone. Acceptable for early-stage or product-market-fit-hunting startups. Unsustainable past Series B.
- Over 24 months: Broken. You cannot scale this without burning cash. Either CAC is too high or LTV is too low. 12 levers to reduce CAC.
Where most SaaS gets it wrong
- Counting only ad spend in CAC. Real CAC includes sales salaries, marketing tool subscriptions, content production, agency fees, paid software, and overhead allocated to growth. Most companies report CAC at 30-50% of the real number.
- Using ARR instead of MRR in the formula. ARR / 12 is not the same as MRR if you have annual prepay discounts. Use the monthly recognized revenue.
- Ignoring gross margin entirely. 80% gross margin means your CAC payback is 25% longer than the simple math suggests. Skipping this overstates your unit economics.
- Not segmenting by acquisition channel. Outbound CAC and inbound CAC are wildly different. Average payback can hide channels burning cash.
Frequently asked questions
What is CAC payback period?
How many months it takes for a new customer to pay back the cost of acquiring them. Calculated as CAC divided by (monthly recurring revenue times gross margin). Healthy SaaS targets 12 to 18 months.
What is a good CAC payback for SaaS?
Under 12 months is excellent. 12 to 18 months is healthy and what most VCs want to see. 18 to 24 months is acceptable for early-stage. Over 24 months means your unit economics are broken.
How is CAC payback different from LTV CAC ratio?
CAC payback measures time to recoup acquisition cost (in months). LTV CAC ratio measures the lifetime value relative to acquisition cost (a multiple). Both matter. Healthy SaaS: payback under 18 months AND LTV CAC ratio above 3.
Does CAC payback include gross margin?
Yes. The proper formula uses gross-margin-adjusted MRR, not raw MRR. If your gross margin is 80% and customer pays $1,000 per month, your math uses $800 per month. Skipping gross margin makes payback look better than it really is.
CAC payback over 18 months?
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