CAC payback and LTV:CAC — what should a €1–20M SaaS actually target?
The two numbers that decide how aggressively a SaaS can buy growth, how to calculate them without flattering yourself, and what they mean for paid ad budgets.
Short answer
Target CAC payback within 12 months for SMB SaaS and 18 months for mid-market, with an LTV:CAC ratio between 3:1 and 5:1. Below 3:1 you are buying unprofitable growth; above 5:1 you are almost certainly under-investing in acquisition.
Key takeaways
- Calculate LTV on gross margin, not revenue — otherwise the ratio flatters you by 20–30%.
- CAC payback in months is a cash-flow metric; LTV:CAC is a profitability metric. You need both.
- A ratio above 5:1 usually means you should be spending more, not celebrating.
- Blended CAC hides the truth; separate paid CAC from organic and referral.
- Annual prepay contracts change everything — they can make a 14-month payback cash-positive on day one.
Calculate the two numbers honestly
CAC payback is fully loaded sales and marketing cost divided by new monthly recurring revenue times gross margin — expressed in months. Fully loaded means salaries, tools and agency fees, not just media spend.
LTV should use gross margin, not revenue: average monthly revenue per account × gross margin ÷ monthly churn. A €200/month plan at 80% margin with 2% monthly churn gives an LTV of €8,000, not €10,000.
| Input | Value |
|---|---|
| ARPA | €200/mo |
| Gross margin | 80% |
| Monthly logo churn | 2% |
| LTV | €8,000 |
| Fully loaded CAC | €2,000 |
| LTV:CAC | 4.0:1 |
| CAC payback | 12.5 months |
What good looks like by segment
Self-serve and SMB products need fast payback because churn is higher and the cash cycle is short. Mid-market and enterprise can tolerate longer payback because contracts are larger, stickier and often prepaid annually.
| Motion | CAC payback | LTV:CAC |
|---|---|---|
| Self-serve / PLG | under 9 months | 4–6:1 |
| SMB sales-assisted | 9–12 months | 3–5:1 |
| Mid-market | 12–18 months | 3–4:1 |
| Enterprise | 18–24 months | 3:1+ |
Why a high ratio is a warning
An LTV:CAC of 8:1 sounds excellent and usually means the company is only harvesting the easiest demand — branded search, inbound referrals, one channel at low spend. Competitors with a 3.5:1 ratio and five times the budget will take the market while the efficient company congratulates itself.
If your ratio is above 5:1 and payback is comfortably inside target, the correct response is to increase acquisition spend until the ratio settles in the 3–4:1 range.
Separate paid CAC from blended CAC
Blended CAC divides all sales and marketing cost by all new customers, including word-of-mouth and organic search. It always looks better than paid CAC and it hides whether paid acquisition is actually working.
Report both: blended CAC for board-level efficiency, paid CAC by channel for the decision about where the next €10,000 goes.
- Blended CAC: total S&M ÷ all new customers
- Paid CAC: paid media + management ÷ paid-sourced customers
- Track paid CAC by channel and by plan tier, not as a single average
- Re-check quarterly; channel CAC drifts as competition changes
What this means for the ad budget
Once you know the maximum CAC your payback target allows, the ad budget becomes arithmetic: target new customers per month × allowable CAC, plus the creative and management cost inside that number.
The remaining question is whether the channels can deliver that volume at that price. That is answered by testing, not by planning — which is why we set a break-even CAC before launch and scale only while the marginal customer stays inside it.
FAQ
Should LTV use gross margin or revenue?
Gross margin. Using revenue inflates LTV by whatever your hosting, support and payment costs are, typically 20–30% for SaaS, and produces a ratio that looks healthy while cash disappears.
How do annual contracts change CAC payback?
Substantially. An annual prepay collects twelve months of cash on day one, so a 12-month payback becomes cash-neutral immediately. Many SaaS companies can justify a materially higher CAC on annual plans than on monthly ones.
What if churn is too new to measure?
Use a conservative placeholder — often 3–5% monthly for SMB — and recalculate quarterly as cohorts mature. Never build a budget on an optimistic churn assumption from a three-month-old cohort.
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