Unit economics measure the profit a business makes from a single customer or unit. The two core metrics are customer acquisition cost (CAC), the average cost to win a customer, and lifetime value (LTV), the total profit that customer generates over time. A healthy business earns several times more in LTV than it spends on CAC.
Why investors obsess over unit economics
Growth only creates value if each customer is profitable. A company can grow revenue quickly while losing money on every sale, which is why investors look past top-line growth to the economics underneath it. Strong unit economics prove that more spending produces more profit, not just more activity.
The two metrics that matter most
How to calculate CAC
Divide your total sales and marketing spend over a period by the number of new customers it produced. If you spend $10,000 and gain 100 customers, your CAC is $100.
How to calculate LTV
Estimate the total gross profit a customer generates before they leave. A simple version multiplies average revenue per customer by gross margin by the average customer lifespan. A higher LTV justifies spending more to acquire customers.
The LTV to CAC ratio and payback period
- LTV to CAC ratio. A common healthy benchmark is roughly 3 to 1. Below 1 to 1 means you lose money on each customer.
- CAC payback period. How many months of revenue it takes to recover CAC. Shorter is better for cash flow.
For a subscription business these ratios sit alongside recurring-revenue measures. Our guide to SaaS metrics extends CAC and LTV with MRR, churn, and net revenue retention.
A worked example
Take a SaaS product at $40 a month per account with an 80% gross margin and 3% monthly churn. Average customer lifespan is 1 ÷ 0.03 ≈ 33 months, so LTV = 40 × 0.80 × 33 ≈ $1,050. If sales and marketing spend works out to a $300 CAC, the LTV:CAC ratio is 3.5 — above the 3:1 benchmark — and CAC payback is 300 ÷ (40 × 0.80) ≈ 9.4 months, comfortable for a venture-backed company and workable for a bootstrapped one. Now watch the leverage hiding in churn: cutting it from 3% to 2% stretches lifespan to 50 months and lifts LTV past $1,600 without spending another marketing dollar — which is why retention, not acquisition, is usually the cheapest growth lever a subscription business has.
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Build my financial modelHow to use them in your plan
Unit economics belong in both your model and your story. Show CAC, LTV, payback, and gross margin in your financial projections and reference them on your traction and business model slides. They are the cleanest evidence that your growth plan can become a profitable business. To pressure-test the contribution margin that sits underneath these numbers, our free break-even calculator shows how price and cost per unit drive the volume you need to turn a profit, and our LTV calculator turns ARPA, margin, and churn into lifetime value and an LTV:CAC ratio. If your unit is a physical product sold through a marketplace, the same per-unit logic applies after platform fees — our Amazon FBA calculatornets referral, fulfillment, and ad costs out of a unit's price to show the true margin.
Common mistakes
- Using revenue instead of gross profit in LTV, which overstates value.
- Ignoring churn, which shortens the customer lifespan and lowers LTV.
- Excluding fully loaded costs from CAC, such as salaries and tools.
These metrics flow naturally out of a clean three-statement model. If you want help building one that an investor will trust, see our financial modeling service.
