Unit Economics
Unit economics is the per-customer profit profile of a business, expressed most commonly as customer lifetime value (LTV) versus customer acquisition cost (CAC). It's used to determine whether a business can profitably acquire customers at scale. It answers the deciding question of any growth-stage startup: does this company make money on each customer, and if it doesn't yet, will it.
The core ratio is LTV divided by CAC. The widely cited benchmark, popularized by David Skok and others in SaaS investing circles, is that LTV:CAC should be at least 3x for a healthy growth-stage business. A 1x ratio means the company recovers acquisition cost but creates no margin. A 2x ratio is marginal. A 3x ratio means each customer creates three dollars of lifetime contribution for every dollar of acquisition cost, which leaves room for the operating costs that are not captured in either number. The other metric paired with this is CAC payback period: how many months it takes for the gross profit from a customer to repay the acquisition cost. Sub-12-month payback is strong for SaaS; 18 months is acceptable; over 24 months is a warning sign. The math has to use real gross margin (not revenue), real fully-loaded CAC (not just paid ads), and an honest retention assumption (not a five-year LTV on a product with 30 percent annual churn).
Ryan's Take
Founders show investors a beautiful LTV:CAC ratio built on optimistic retention and a stripped-down CAC. Investors stopped believing those numbers years ago. Build the unit economics the way the math actually works: real gross margin, every salary and tool in CAC, and an LTV based on the retention curve you have, not the one you want. If the honest ratio is under 3x, that is fine, but you raise that round on a plan to fix it, not on a slide that hides it. The unit economics you fake at Series A become the argument you lose at Series B.
What founders get wrong: Computing LTV on revenue instead of gross profit. LTV must use gross margin, because the part of revenue that goes to cost of goods sold (hosting, payment processing, support) is not available to repay CAC. Skipping that adjustment doubles or triples the apparent LTV.
Related: Customer Acquisition Cost (CAC) · Lifetime Value (LTV) · Burn Rate · Product-Market Fit
FAQ
What is the LTV:CAC ratio?
The ratio of customer lifetime value to customer acquisition cost. The widely cited healthy benchmark is at least 3x, meaning each customer produces three dollars of gross-margin lifetime value for every dollar of acquisition cost.
What is a good CAC payback period?
For SaaS businesses, under 12 months is strong, 18 months is acceptable, and over 24 months is a warning sign. The payback period uses gross profit, not revenue, to determine how fast the customer repays the cost of acquiring them.
Why is unit economics important?
Because growth without unit economics is just burn. A company can grow revenue at any cost; the question is whether each new customer adds margin or subtracts it. Investors price growth-stage rounds on the answer.
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