If you only ever look at one number to judge whether your growth is efficient, make it the LTV:CAC ratio. It compares the lifetime value of a customer against the cost to acquire them — and it instantly tells you whether your growth engine is a profit machine or a money furnace.
The Two Numbers
LTV (Lifetime Value) is the total profit you expect from one customer over their whole relationship with you. A simple version: monthly revenue per customer × gross margin ÷ monthly churn.
CAC (Customer Acquisition Cost) is your total sales and marketing spend divided by the number of new customers it produced. Fully loaded means including ad spend, salaries, tools — not just ads.
The 3:1 Rule
The classic benchmark is 3:1 — a customer should be worth about three times what you paid to acquire them. Why three? Because your LTV must still cover product costs, overhead, and profit after paying for acquisition. At 1:1 you lose money on every customer. At 2:1 you are probably barely breaking even after overhead.
How to Read Your Ratio
- Under 1:1 — You pay more for a customer than they ever return. Stop scaling and fix the product or pricing.
- 1:1 to 2:1 — Marginal. Growth eats cash. Improve margins or cut CAC before scaling.
- Around 3:1 — Healthy. This is the sweet spot for efficient growth.
- 5:1 or higher — Surprisingly not ideal. It usually means you are under-investing in growth and leaving market share to competitors.
Worked Example
A SaaS with $100 average monthly revenue per customer, 80% gross margin, and 2% monthly churn:
- LTV = $100 × 0.80 ÷ 0.02 = $4,000
- CAC = $1,200
- Ratio = 4,000 ÷ 1,200 = 3.3:1 — healthy, scale it.
How to Improve the Ratio
- Raise LTV: improve pricing, reduce churn, and add expansion revenue (upsells). Churn cuts are the cheapest LTV gains.
- Lower CAC: double down on your best-performing channel, improve landing page conversion, and build organic channels (SEO, content) that compound.
- Fire bad segments. If one customer segment has a terrible ratio, stop buying it — a lower CAC with worse customers is not a win.
Calculate your ratio in 30 seconds.
Enter your revenue, margin, churn and acquisition spend — get LTV, CAC and the ratio instantly.
Open LTV:CAC Calculator →The ratio only matters in context. Pair it with your MRR and SaaS break-even to see when efficient growth actually turns into profit.