A business can grow revenue quickly and still be doomed if it loses money on every customer. Unit economics is the discipline of examining one unit, often a single customer, to see whether the fundamental model works. It centers on two figures: what it costs to win a customer and what that customer is worth over time. When these numbers are healthy, growth compounds value; when they are not, growth just accelerates losses.
Customer acquisition cost
Customer acquisition cost, or CAC, is the total sales and marketing spend divided by the number of new customers it produced. If you spent 10,000 dollars on ads and outreach to win 100 customers, your CAC is 100 dollars. A rising CAC signals that your channels are saturating or your message is weakening. Knowing CAC keeps you from celebrating growth that is actually being bought at a loss.
Lifetime value
Lifetime value, or LTV, estimates the total contribution margin a customer generates before they leave. It combines how much they spend, how often, the margin on that spending, and how long they stay. A subscription that nets 30 dollars a month for an average of 20 months has an LTV of 600 dollars. LTV built on contribution margin, not revenue, is the honest version, because it counts only money you keep.
The LTV to CAC ratio
Comparing LTV to CAC shows whether each customer earns back more than they cost to acquire. A widely cited healthy benchmark is roughly three to one, meaning a customer is worth about three times what you paid to get them. A ratio near one to one means you barely recover your acquisition spend, leaving nothing for fixed costs or profit. Far above three to one may even suggest you are underinvesting in growth.
Payback period and its limits
CAC payback period measures how many months of contribution margin it takes to recover the acquisition cost. A short payback frees cash to reinvest sooner, which matters enormously for a business funding its own growth. Remember that unit economics rests on assumptions about churn and margins that can shift, so revisit them regularly. Strong unit economics is necessary for a durable business, but it does not guarantee positive cash flow while you are scaling.
An app spends 60 dollars to acquire a subscriber who nets 12 dollars a month and stays 18 months, an LTV of 216 dollars. The LTV to CAC ratio is 3.6 to 1, and the CAC payback period is five months, both signs of a sound model.
Key takeaways
- Unit economics examines the cost and value of a single customer or sale.
- CAC is total acquisition spend divided by new customers won.
- LTV is the lifetime contribution margin a customer generates before leaving.
- An LTV to CAC ratio around three to one is a common healthy benchmark.
Common mistakes
- Building LTV on revenue instead of contribution margin, overstating each customer's worth.
- Ignoring churn, which shortens customer lifetime and shrinks LTV.
- Scaling ad spend before confirming the LTV to CAC ratio is healthy.
FAQ
What is a good LTV to CAC ratio?
Around three to one is often cited as healthy, though the right target varies by industry and growth stage.
Why use contribution margin in LTV rather than revenue?
Because only the margin is money you keep; using revenue makes a customer look far more valuable than they truly are.