SaaS Financial Model: The Metrics Investors Check
The metrics a SaaS financial model must produce - MRR, churn, net revenue retention, CAC, LTV and payback - with a worked unit-economics example.
Key takeaways
- A SaaS model forecasts customers as cohorts: acquired, paying, expanding and churning.
- With $500 ARPA, 80% margin, 2% churn and $6,000 CAC: LTV is $20,000, LTV/CAC about 3.3x, payback 15 months.
- Lifetime value is highly sensitive to churn, so churn assumptions must match real history.
A SaaS financial model is built around recurring revenue. Instead of forecasting sales as a single line, it tracks customers as a cohort that is acquired, pays every month, expands and eventually leaves. The metrics investors look for fall out of that structure, and they expect to be able to trace each one back to the underlying customer numbers.
Revenue metrics
- Monthly recurring revenue (MRR) and annual recurring revenue (ARR): the contracted subscription run-rate, excluding one-off fees.
- New, expansion, contraction and churned MRR: the four movements that explain the change in MRR each month.
- Net revenue retention: what a cohort of customers pays a year later as a percentage of what it paid at the start, including upgrades and losses.
Churn
Churn can be measured by customers lost or by revenue lost, and the two often differ. A company losing many small customers while large ones expand can have high customer churn and healthy revenue retention. A model should show both and make clear which one drives the forecast.
Unit economics: a worked example
Average revenue per account is $500 a month, gross margin is 80%, monthly customer churn is 2% and the cost to acquire a customer is $6,000.
- Lifetime value: $500 x 80% / 2% = $20,000
- LTV to CAC ratio: $20,000 / $6,000 = about 3.3x
- CAC payback: $6,000 / ($500 x 80%) = 15 months
Note how sensitive lifetime value is to churn. At 3% monthly churn the same customer is worth about $13,300 and the ratio falls to roughly 2.2x.
How the model is structured
Build the customer base month by month: opening customers, plus new customers from the sales and marketing plan, less churn. Apply pricing and expansion to get MRR. Drive costs from their real causes - hosting from usage, support from customer numbers, sales headcount from the pipeline it has to generate. Then link everything to cash, including the timing difference between annual billing and monthly revenue recognition.
What investors test
- Whether new customer growth is consistent with the sales and marketing spend.
- Whether churn assumptions match the company's own history.
- How many months of cash runway the plan leaves, and when the next raise is needed.
- What happens to runway if growth is slower or churn is higher.
For the wider picture of what a raise requires, see what investors expect from a startup financial model. We build SaaS models as part of our financial modelling service.
Frequently asked questions
What is a good LTV to CAC ratio?
A ratio of about 3x is widely used as a reference point, with a payback period under about 12 to 18 months. The right figure depends on growth stage, margin and how reliable the churn data is.
What is the difference between MRR and revenue?
MRR is the recurring subscription run-rate at a point in time. Recognised revenue is an accounting figure for a period and can include one-off fees and services. A model should show both and reconcile them.
What is net revenue retention?
It is the revenue from a group of customers one year on, divided by their revenue at the start, including upgrades, downgrades and cancellations. A figure above 100% means existing customers are growing faster than they are leaving.