With margin adjustment and months-to-payback, which is the more useful number at solo scale. Enter real cash spend only.
Enter real cash spend only. If acquisition is mostly your own time, the honest CAC is near zero and the ratio will not tell you anything.
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An LTV:CAC calculator is only as good as its two inputs, and both are shaky early. LTV divides ARPU by churn. At fifty customers, one cancellation moves churn by two points and LTV by hundreds of dollars — the output looks precise and moves on individual circumstances.
CAC is worse. If your acquisition is writing posts and emailing people individually, the honest cash cost is close to zero. Count your time at some invented hourly rate and the ratio becomes a function of a number you made up.
That is why this calculator asks for cash spend only. A CAC of zero is not a broken input — it is the correct answer, and it tells you the ratio is not the metric to steer by. LTV:CAC at solo scale covers what to use instead.
How many months of a customer's subscription it takes to earn back what you spent acquiring them. It uses the same inputs and makes fewer assumptions, because it does not require projecting a lifetime.
| Payback period | Reading |
|---|---|
| Under 3 months | Strong. You can reinvest quickly. |
| 3–12 months | Workable for a bootstrapped product |
| Over 12 months | You are funding growth from savings |
For a business with no outside capital, payback matters more than the ratio because it determines how fast you can recycle cash into more acquisition. A 4:1 ratio with an eighteen-month payback is a cash-flow problem regardless of how healthy it looks.
Revenue is not profit. A customer paying $79 a month against $12 of hosting, payment fees and AI inference contributes $67, and using the gross figure overstates LTV by roughly the margin gap.
For conventional SaaS, margins of 80–90% mean the adjustment is small. For AI products with real inference cost it can be substantial, which is one reason AI pricing needs a usage-linked unit — the value metric framework covers that decision.
If your CAC comes out at zero because you have never spent money on acquisition, that is useful information rather than a gap. It means your constraint is hours, not cash, and a metric denominated in money cannot see the constraint that binds you.
Deciding whether to spend more on a channel that already works. If you know that $600 reliably produces six customers, the ratio tells you whether $1,200 would be a good idea.
It is not for judging whether your business is healthy, and it is not a benchmark to hit. Plenty of profitable solo products have never computed it, because they have never bought a customer.
Once you are spending, it becomes genuinely useful alongside a stable churn figure — the churn benchmark check covers whether your rate is stable enough to build on, and the MRR projection calculator covers the ceiling your churn rate implies.
LTV is ARPU divided by monthly churn rate, multiplied by gross margin. CAC is cash acquisition spend divided by customers acquired. The ratio is LTV divided by CAC, and the commonly quoted benchmark is 3:1.
No. Counting your time at an invented hourly rate makes the ratio a function of a number you made up. If your acquisition is entirely your own effort, the honest CAC is zero — which correctly tells you the ratio is not your steering metric.
It makes fewer assumptions, because it does not require projecting a customer lifetime, and it is denominated in cash and time. A 4:1 ratio with an eighteen-month payback is a cash-flow problem regardless of how healthy the ratio looks.
Yes. A customer paying $79 against $12 of hosting, fees and inference contributes $67, so using the gross figure overstates LTV. For conventional SaaS at 80–90% margin the adjustment is small; for AI products with real inference cost it can be substantial.
Under three months is strong and lets you recycle cash quickly. Three to twelve is workable. Over twelve months means you are funding growth from savings for more than a year per customer, which most bootstrapped products cannot sustain.
Bring your churn, ARPU and what you actually spend. Marcus tells you which number to steer by at your stage.
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