Your inputs
Core metrics
ARR-
Customers-
LTV (gross)-
LTV:CAC ratio-
CAC Payback (months)-
Annual churn rate-
Net Revenue Retention-
Rule of 40
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MRR · ARR · Churn · LTV · CAC Payback · NRR · Rule of 40 — all in one place.
This calculator turns raw subscription numbers into the standard set of SaaS operating metrics: MRR and ARR, monthly churn rate, customer lifetime value, CAC payback period, net revenue retention, and the Rule of 40 score. For API and cloud businesses, these figures only mean something once gross margin is applied — inference, compute, bandwidth, and egress costs sit inside cost of revenue, so a nominal $50k MRR may contribute far less toward recovering acquisition spend. Entering your real gross margin alongside churn and expansion MRR shows how much contribution each customer actually generates, how long that customer is likely to stay, and whether your growth rate justifies your current burn.
LTV and payback should be measured on gross profit, not revenue, because usage-based infrastructure costs are consumed before any money is available to repay acquisition spend. At 80% margin, $100 ARPU contributes $80/month toward CAC; at 45% margin — common for inference-heavy AI products — it contributes only $45, roughly doubling the payback period for the same CAC.
For B2B SaaS, CAC payback under 12 months is generally considered healthy and under 6 months is strong, while 18 months or more signals an acquisition efficiency problem. An LTV:CAC ratio around 3:1 is the common benchmark; much lower suggests overspending on acquisition, and much higher may mean you are underinvesting in growth.
Net revenue retention combines expansion MRR from existing customers against churned and contracted revenue, so NRR above 100% means the existing base grows even with no new logos — common in usage-based API pricing where customers scale consumption over time. The Rule of 40 score is year-over-year growth rate plus profit margin, with 40 or above treated as the threshold for balanced growth and efficiency.