SaaS Financial Model: MRR Build, LTV/CAC, 36-Month Cash – Excel XLSX

BENEFITS OF THIS DOWNLOADABLE EXCEL DOCUMENT

1. MRR built month by month from new and churned revenue as separate lines, so a churn change compounds through the curve instead of just changing an end number.
2. Lifetime value computed from ARPU, gross margin and churn - the real definition - so it responds correctly when the margin moves.
3. Eighteen plain-English integrity tests inside the file, all passing and all live, including that ending MRR can never go negative.

SAAS EXCEL DESCRIPTION

SaaS Financial Model: MRR Build, LTV/CAC, 36-Month Cash is an Excel template (XLSX) available for immediate download upon purchase.

The common failure in a SaaS spreadsheet is that the growth projection and the unit economics are two separate pieces of arithmetic that never meet. Someone types a growth rate into an MRR curve, then types an LTV and a CAC into a box underneath, and nothing forces the two to be consistent. This model builds both from one set of assumptions, so a change to churn moves the MRR curve and the lifetime value and the payback period at the same time, in the directions they actually move.

The example that ships in the file starts at $50,000 of MRR, adds 5% of the month's starting MRR in new business and loses 2% to churn, with ARPU of $50, a 75% gross margin, CAC of $250, sales and marketing at 30% of revenue, $80,000 of fixed monthly operating cost and $200,000 of opening cash.

On those numbers: lifetime value $1,875, LTV to CAC 7.5x, CAC payback 6.7 months, ending MRR in month 36 of $144,914, and a run-rate revenue of $1,738,967.

Three things this model does that comparable SaaS templates do not.

First, the MRR schedule is a real build, not a growth rate applied to a total. Every month shows starting MRR, new MRR, churned MRR and ending MRR as four separate lines, and each month starts exactly where the previous one ended. That structure is what lets you see the compounding effect of a churn change rather than just a different end number – and it is what an investor will ask to see.

Second, lifetime value is computed the way the metric is actually defined – ARPU times gross margin divided by monthly churn – rather than as revenue times an assumed retention in months. The distinction matters: the version in this file falls correctly when the gross margin falls, which the shortcut version does not.

Third, the cash line is driven by the P&L rather than by a separate guess. Revenue is the month's ending MRR, cost of sales follows from the gross margin, operating costs are sales and marketing as a share of revenue plus the fixed block, EBITDA falls out, and the cash balance is opening cash plus cumulative cash flow. One chain, no parallel arithmetic.

What is inside. Seven sheets. ReadMe with a colour key and a sheet guide. Assumptions – starting MRR, monthly new and churn rates, ARPU, gross margin, CAC, sales and marketing as a share of revenue, fixed operating cost, months to model and opening cash. MRR Schedule – 36 months of starting, new, churned and ending MRR. P&L – revenue, cost of sales, gross profit, sales and marketing, fixed costs, total operating expenses and EBITDA for every month. Cash Flow – monthly net cash flow, the cumulative total and the running cash balance. Metrics – LTV, LTV/CAC, CAC payback in months, ending MRR and run-rate revenue. Checks – eighteen pass/fail tests.

How you know the numbers are right. The Checks sheet runs eighteen tests inside the workbook and all eighteen pass in the shipped file. In plain English: that ending MRR is starting plus new less churned in every month, that each month opens where the last one closed, that new and churned MRR are the stated rates on the month's starting balance, that revenue in the P&L is the month's ending MRR, that EBITDA is gross profit less total operating expenses, that the cash balance is opening cash plus the cumulative flow, that LTV is ARPU times gross margin over churn, that the LTV to CAC ratio divides correctly, that CAC payback is acquisition cost over monthly gross profit per customer, that churn stays below 100% so the series does not invert, and that ending MRR is never negative in any month.

Separately, every output was re-derived in an independent script using different arithmetic. That verification covered this model together with three others in the same family – 691 comparisons in all, no disagreements.

What this model does not do. It works at the MRR level with a single blended ARPU and a single churn rate. There are no cohorts, no tiers or plans with separate pricing, no expansion or contraction MRR as distinct lines, no headcount plan, and no balance sheet – the cash view is a running balance, not a three-statement model. If you need cohort retention curves or a plan-by-plan build, that is a different and much larger file. If you need a clean, auditable 36-month MRR and cash picture with unit economics that move with it, this is built for that and shows its work.

Source: Best Practices in SaaS, Integrated Financial Model Excel: SaaS Financial Model: MRR Build, LTV/CAC, 36-Month Cash Excel (XLSX) Spreadsheet, Paweł Dudek, Balancewright