Churn & LTV calculator
Back-of-the-envelope unit economics for SaaS. Plug in ARPU and churn — get lifetime, LTV, and whether you can afford to acquire customers. Pairs with the MRR calculator for full funnel math.
Benchmarks: 3–5% monthly churn is normal for B2C SaaS. Under 1% monthly is great for B2B. Gross margin defaults to 85% — typical for software after hosting and payment fees.
Avg customer lifetime
1 ÷ monthly churn rate
LTV (gross margin)
ARPU × margin ÷ churn
LTV : CAC
3:1 is the classic rule of thumb
CAC payback
CAC ÷ monthly contribution
The 3:1 LTV:CAC rule is a shorthand, not physics. It ignores expansion revenue, payback timing, and whether churn is getting better or worse. Use it as a smell test, not a fundraising slide.
Retention curve (100-customer cohort)
| Months | Customers left | % of cohort |
|---|---|---|
About this tool
Simple exponential churn model: every month, a fixed percentage of customers leave. Real cohorts are messier — early churn spikes, annual plans behave differently — but this answers whether the math is in the right ballpark.
LTV here is contribution margin LTV (after gross margin), not revenue LTV. For MRR projections with traffic and conversion, use theMRR calculator.