The most quoted ratio in SaaS, built from two numbers a small product cannot measure reliably. Here is what breaks, and what to use until it does not.
LTV:CAC is the most quoted ratio in SaaS and one of the least useful to a solo founder. Both halves of it are unreliable below roughly $5k MRR, and a ratio built from two unreliable numbers is not a weak signal — it is a confident-looking guess.
LTV:CAC becomes useful when you start spending money — not time — on acquisition.
This page is about why the ratio misleads at small scale, and what to use until it does not.
Lifetime value is normally calculated as average revenue per account divided by churn rate. That division is where it falls apart.
At thirty customers, one cancellation is a churn rate of roughly 3.3% and two is 6.7%. Feed those into the formula and your LTV halves because one person's circumstances changed. The output swings by hundreds of dollars on a difference that carries no information about your business.
It gets worse with young products. LTV assumes your current churn rate continues indefinitely, but a product that launched eight months ago has no customer who has been around for two years. You are extrapolating a lifetime from a sample where nobody has lived one.
Customer acquisition cost is straightforward when you buy traffic. It is close to meaningless when your acquisition is writing posts, answering questions in a community, and emailing people individually.
Two options, both bad. Count your time at zero and CAC is near-zero, which makes any LTV:CAC ratio look spectacular and tells you nothing. Or price your time at some hourly rate and the number becomes a function of a figure you invented.
Most solo founders under $5k MRR are in exactly this position. Their real constraint is hours, not money, and a ratio denominated in money cannot see the constraint that binds them.
The 3:1 benchmark is real and it is sound — for the companies it was derived from. Those companies have paid acquisition channels, sales teams, multi-year contracts, and enough customers for churn to be a stable input.
Applying it to a product with forty self-serve customers and no ad spend imports an assumption set that does not hold. A ratio of 8:1 at that scale usually means you are undercounting your time, not that you have found an exceptional business.
The general problem — benchmarks drawn from companies two orders of magnitude larger than yours — runs through most published SaaS data. The benchmarks that do apply at solo scale covers which figures survive the translation.
Two measures that work with the data a small product actually has.
Months to payback, on cash only. If you spent money to get a customer, how many months of their subscription does it take to earn that back? Count only real spend — ads, tools, sponsorships. If you spent nothing, the answer is zero months and the metric correctly tells you the constraint is elsewhere.
Churn by cohort, in months. Rather than converting churn into a lifetime figure, look at how many of each monthly cohort are still active at month three and month six. The shape of that curve tells you what LTV was trying to tell you, without the false precision.
| Stage | Use | Ignore |
|---|---|---|
| Under $1k MRR | Activation and conversations | LTV, CAC, and the ratio |
| $1k–$5k MRR | Cohort retention at month 3 and 6 | LTV:CAC |
| $5k–$10k MRR | Months-to-payback on real spend | LTV, unless churn is stable |
| $10k+ MRR | LTV:CAC starts to be meaningful | — |
If you need LTV for a specific decision — whether an annual plan discount is worth it, say — use a deliberately conservative churn figure and treat the answer as a range rather than a number. A pessimistic estimate that informs one decision is fine. A precise-looking figure on a dashboard is not.
Three conditions, and you need all three. Churn has been stable within a percentage point or so for two quarters. You are spending real money on at least one acquisition channel. And you have enough customers that a single cancellation moves your churn rate by less than a point — roughly a hundred.
Until then, the useful questions are different: are people activating, do they convert, and do they stay. The four metrics that matter under $10k MRR covers the short list, and the $1k to $10k playbook covers the stage where this changes.
If acquisition spend is what you are weighing up, the channel decision comes before the ratio — see how to pick one channel and stick to it.
Rarely below $5k MRR. LTV needs a stable churn rate that a product with fifty customers does not have, and CAC needs real spend rather than your own time. A ratio built from two unreliable inputs looks precise while carrying almost no information.
LTV divides revenue per account by churn rate, and at thirty customers a single cancellation moves churn from roughly 3.3% to 6.7%. That halves your LTV based on one person's circumstances changing, which tells you nothing about the business.
Not directly. The benchmark comes from companies with paid channels, sales teams and enough customers for churn to be stable. At forty self-serve customers with no ad spend, a ratio of 8:1 usually means you are undercounting your own time.
Months to payback counted on real cash spend only, and churn by monthly cohort at month three and month six. The shape of the cohort curve tells you what LTV was trying to say, without inventing precision the data cannot support.
When three things are true together: churn has been stable within about a percentage point for two quarters, you are spending real money on at least one acquisition channel, and you have enough customers that one cancellation moves churn by less than a point.
Give Marcus your customer count, churn and acquisition spend. You get the measures that fit your stage and the one to act on.
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