SaaS Unit Economics Calculator
See whether an account pays back what it cost to win, how long that takes, and what the same customer is worth over their life.
What this calculates
This computes three numbers from four inputs: the ratio of lifetime value to acquisition cost, the months until an account has repaid its acquisition cost in gross profit, and the lifetime value itself. Lifetime is derived from your churn rate rather than observed, which makes every figure here a projection of the present rather than a measurement of the past.
At typical inputs for a B2B SaaS company with a $12,000 acquisition cost, $840 monthly ARPU, 2.5% monthly churn and an 80% gross margin, the LTV to CAC ratio is 2.2×, payback is 18 months and lifetime value is $26,880.
Your numbers
Acquisition
The account
Results update as you type. Nothing is sent anywhere, the calculation runs in your browser.
Economics health
LiveLTV : CAC
2.2×
target 3.0×
Payback
18 mo
target 12 months or less
Customer LTV
$26,880
Cumulative gross profit per customer, net of CAC
- Gross profit per account
- $672 /mo
- LTV if churn were 2.0%
- $33,600
Watch
Both numbers miss for the same reason: the gross profit one account produces each month is small next to what it costs to win. Cutting acquisition spend fixes the ratio and stalls growth. Raising price or margin fixes both at once, which is why pricing is usually the first place to look and headcount is the last.
Pressure-test this against your real numbers
Thirty minutes on which of the four inputs is actually movable this quarter.
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How is this calculated?
Monthly gross profit per account is revenue times gross margin. Payback is acquisition cost divided by that. Lifetime value treats churn as a constant monthly hazard, so the expected life of an account is one divided by the churn rate and its value is gross profit times that life. The curve below shows the same arithmetic month by month, starting at minus the acquisition cost.
Formula
Gross profit per month = ARPU × gross margin Payback = CAC ÷ gross profit per month LTV = gross profit per month ÷ monthly churn LTV : CAC = LTV ÷ CAC Cumulative(m) = −CAC + gross profit × (1 − (1 − churn)m) ÷ churn
- Churn is a constant monthly hazard applied to every account equally. Real cohorts churn hardest early and then flatten, which makes this understate the value of accounts that survive their first year.
- The payback figure ignores churn during the payback window. Breakeven on the curve accounts for it, which is why the dot sits later than the payback metric.
- CAC is fully loaded: sales salaries and commission, marketing spend, and the tools both use, divided by new accounts won in the same period.
- Expansion revenue is excluded. If you run net revenue retention above 100%, lifetime value here is a floor rather than an estimate.
- The targets shown, three times CAC and twelve months, are the conventions investors ask about. They are not derived from your inputs.
When this number misleads
A blended CAC across self-serve and sales-led accounts produces a ratio that describes neither. If a quarter of your accounts arrive with no sales involvement, they are subsidizing a channel that may not work at all, and the average hides it completely. Split the inputs by channel and run this twice. The two answers are usually far enough apart to change what you do next. If the lifetime value itself is the part you are unsure about, the Customer Lifetime Value Calculator takes it apart input by input.
Questions founders ask about this
Why is breakeven on the curve later than the payback figure?
Because payback divides two numbers and assumes the account survives. The curve applies churn every month, so the expected profit from month twelve is worth less than the profit from month one. The gap between the two is a fair measure of how much your churn rate is costing you.
Should I use logo churn or revenue churn here?
Logo churn, because the model is about the life of one account. Feeding revenue churn in will mix expansion and contraction into a number that is meant to describe survival, and if your net revenue churn is negative the lifetime value becomes infinite.
Is three times CAC really the bar?
It is the convention, not a law. Three assumes you want a third of lifetime gross profit left over after acquisition and delivery. A company with very long contracts and low churn can operate happily below it. A company raising money will still be asked about it.
Do you store what I enter?
No. The calculation runs in your browser and nothing is transmitted. Your last inputs are saved in your own browser so the page remembers them when you return. If you use the email field, only the result summary and your address are sent.
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