Profit Per Customer, Explained.

Unit economics is the question of whether a single customer makes you money. This calculator runs the full chain from average revenue per user (ARPU), through gross margin and contribution profit, to LTV, CAC payback, and the LTV:CAC ratio. The point is to see where the leak is: bad unit economics can fail at any link, and the dashboard view tells you which one before you pour more spend on top.

ARPU is the average monthly revenue per paying account. Gross margin is what's left after the direct cost of serving that customer (hosting, third-party APIs, support, payment processing); the rest is your contribution dollars. LTV is contribution profit divided by monthly churn rate. CAC payback is the time in months for the contribution profit to repay the acquisition cost. The LTV:CAC ratio is just LTV divided by CAC. The widely-cited benchmarks come from David Skok's SaaS Metrics 2.0.

For a healthy SaaS business in 2026: gross margin 75%+ for pure software (60%+ if you have services attached); CAC payback under 12 months for venture-backed growth (under 18 for capital-efficient SaaS per the OpenView Benchmarks); LTV:CAC at 3:1 minimum and 4:1+ as a sign you can spend more on acquisition. Below 1:1 you're burning money on every customer; above 6:1 you're under-investing in growth.

Three common errors. Using revenue instead of contribution profit for LTV inflates it by 25-40%; the ratio becomes meaningless. Calculating CAC blended across organic and paid channels hides the truth about paid efficiency: blended CAC at a developer-led product is often half of paid-only CAC because organic does most of the work. Treating annual churn as monthly churndivides LTV by twelve. Run it both ways if you're not sure which churn cohort window you have.

Quarterly, once you have at least 100 paying customers and 6 months of churn data. Earlier than that the percentage-based metrics swing on every cancellation. If unit economics break, fix in order: gross margin first (it caps everything downstream), then CAC, then churn. The LTV:CAC calculator drills into the ratio specifically; the SaaS metrics calculator goes broader on growth and retention.