Oct 08, 2026 by Offer

Unit economics: Answer Guide 2027

Unit economics measure the profitability of a single "unit" of a business — one customer, one order, one store — expressed as lifetime value (LTV) versus customer acquisition cost (CAC). Healthy unit economics mean each unit makes money before scale; without them, growth multiplies losses. In a unit economics interview, define LTV/CAC, give the benchmark, and explain the scale caveat.

Unit Economics Interview Questions: What They Test

The LTV/CAC ratio is the headline: lifetime value divided by acquisition cost, with 3:1 commonly cited as the healthy threshold — though norms may vary by business model. The CAC payback period (months to recover acquisition cost) is the companion metric investors watch alongside it.

Interviewers want the judgment behind the numbers. Unit economics must be computed on contribution margin — revenue minus variable costs — not gross revenue, and LTV depends on churn assumptions that deserve scrutiny. The deeper point: good unit economics are necessary but not sufficient — fixed costs, overhead, and working capital can still sink a business that looks great per-unit.

How to Answer a Unit Economics Interview Question

Define it. "Unit economics = the profit per customer (or order, or store) — LTV versus CAC is the standard expression."
State the benchmark. "LTV/CAC above 3 is the common healthy threshold, with payback ideally under 12 months — norms may vary."
Show the math. "LTV = ARPU × gross margin / churn rate; CAC = total sales and marketing spend / new customers acquired."
Add the caveat. "Per-unit profit must cover fixed costs — great unit economics with insufficient scale still loses money."

Common Mistakes in Unit Economics Interview Answers

Using revenue instead of margin. LTV must be built on contribution or gross margin — revenue-based LTV is meaningless.
Ignoring churn sensitivity. Small churn assumptions swing LTV wildly — always stress-test the churn input.
Assuming scale fixes everything. Scale improves fixed-cost leverage, not unit economics — if each unit loses money, growth deepens the hole.

Unit economics questions test whether you can reduce a business to its atomic profit engine — a core skill for investing and strategy roles.

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FAQ

Q: What is a good LTV to CAC ratio? A: 3:1 or higher is the widely cited healthy benchmark, meaning each customer returns three times its acquisition cost over its lifetime — though norms may vary.

Q: How do you calculate LTV? A: A common formulation is average revenue per user times gross margin divided by the churn rate, giving the expected lifetime profit per customer.

Q: What is CAC payback period? A: The number of months of customer contribution margin needed to recover the acquisition cost — shorter is better for cash efficiency.

Q: Can a company with good unit economics still fail? A: Yes — if fixed costs and overhead exceed total unit contribution, or if working capital needs outrun cash generation.

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