SaaS Unit Economics & LTV:CAC Diagnostic

Revenue growth can hide a business that loses money on every customer it acquires. This is the diagnostic that catches it.

Reading This Tool

How To Use This Calculator

Enter your MRR, ARPU, monthly churn rate, CAC and gross margin, numbers you should already have from your billing and ad platforms.

The first chart shows how long it takes a new customer's gross profit to repay what it cost to acquire them; the second shows how fast your customer base actually shrinks each month at your current churn rate. An LTV:CAC ratio under 3x is the standard signal that acquisition economics need attention before spending more on growth.

Your Inputs

Monthly Recurring Revenue $80,000

Average Revenue Per User (ARPU/mo) $400

Monthly Churn Rate 3%

Customer Acquisition Cost (CAC) $1,800

Gross Margin 80%

LTV here is modeled the standard simple way: (ARPU × gross margin) ÷ monthly churn rate. Real LTV models often add discounting and cohort-specific churn curves, this gives you the directionally correct number fast.

Unit Economics

LTV : CAC Ratio

0.0x

Customer Lifetime Value

CAC Payback Period

0 mo

Avg. Customer Lifetime

0 mo

Active Customers (Est.)

Cumulative Gross Profit Per Customer vs. CAC

Cumulative Gross Profit / Customer CAC Recovered

Cohort Retention Curve, 24 Months

This model assumes flat ARPU and a constant monthly churn rate per cohort, real businesses see churn curves flatten over time as weaker-fit customers leave early. Treat this as a fast diagnostic, not a board-deck-final metric.

If this ratio is under 3x, the fix is usually structural.

Request a CFO Strategy Session →