The SaaS numbers that matter
Software-as-a-service businesses live on a handful of recurring-revenue metrics. This calculator turns your plans, customer counts and one month of movement into MRR, ARR, ARPA, churn, net revenue retention, customer lifetime, LTV, CAC, LTV to CAC and CAC payback, then projects the next twelve months at the same pace so you can see where the current trend leads.
Definitions
- MRR is monthly recurring revenue: plan price times customers, summed across plans. ARR is MRR times twelve.
- ARPA is average revenue per account, which is MRR divided by customers.
- Logo churn is customers lost divided by customers at the start. Revenue churn also counts downgrades.
- Net revenue retention is starting revenue, minus lost and downgraded revenue, plus expansion, divided by starting revenue. Above 100% means existing customers grow on their own.
- LTV is ARPA times gross margin divided by churn. CAC is sales and marketing spend divided by new customers.
- CAC payback is how many months of gross profit it takes to earn back the cost of acquiring a customer.
Reading the results
A common rule of thumb is LTV to CAC of about 3 to 1 or better and CAC payback under a year, but the right targets depend on your market, price and cash position. Churn is the number to watch: small differences compound heavily over a year. Use real, recent figures rather than a best-case month, and run it again for each month to see the trend.
Limits of the model
The projection assumes constant pricing, a fixed number of new customers each month and a constant churn rate, and it ignores seasonality, annual plans, trials and discounting. LTV formulas that divide by churn are very sensitive when churn is low. Treat the output as a quick planning aid, not an investor-ready financial model.