Unit economics is the discipline of asking, for every business: does each transaction make money? Not on average, not after some imagined future scale, not after assuming overhead is "fixed and will dilute" — but right now, on a clean per-unit basis. Businesses with strong unit economics can grow into profitability. Businesses with broken unit economics lose more money the bigger they get. This guide covers the formulas, the benchmarks by business model, and how to use unit economics to make pricing, acquisition, and product decisions.
The Three Core Numbers
- Contribution margin per unit. Revenue per unit minus variable cost per unit.
- Customer Acquisition Cost (CAC). All sales and marketing spend in a period divided by net new customers in the same period.
- Lifetime Value (LTV). The total gross profit you expect from a customer across their entire relationship with you.
From these three numbers, every meaningful unit-economics ratio is derived: LTV/CAC, payback period, contribution margin %, gross margin %.
Contribution Margin Per Unit
For a product business:
Contribution Margin = Price - (Cost of Goods + Variable Selling Costs + Returns Allowance)For a subscription business, the unit is a customer-month or customer-year, and contribution margin includes hosting, support, and processing per customer.
Worked example — a DTC skincare brand:
| Line | Per unit |
|---|---|
| Average order value | $48 |
| COGS (product + packaging) | −$12 |
| Shipping | −$6 |
| Payment processing (2.9% + $0.30) | −$1.69 |
| Returns allowance (5%) | −$2.40 |
| Contribution margin per order | $25.91 (54%) |
CAC — and How Most People Calculate It Wrong
The textbook formula:
CAC = (Sales + Marketing spend in period) / Net new customers in periodThe three most common ways to get this wrong:
- Counting only paid-media spend. Real CAC includes salaries of the people running marketing, the CRM, the tooling, the agency fees, the salaries of any sales team.
- Counting gross new customers instead of net. If you acquired 200 customers but lost 80 to churn in the same period, your net is 120 — and that's what CAC should be calculated against if you're tracking growth.
- Using a too-long attribution window. If you measure CAC over 6 months but customers convert in 14 days, you're counting investment that hasn't paid off yet against customers who already paid.
LTV — and Why Most LTV Numbers Are Fantasy
LTV is the gross profit a customer generates over their entire lifetime with you. The simple formula for a subscription business:
LTV = (ARPU × Gross Margin %) / Monthly Churn RateFor a $30/month customer with 80% gross margin and 5% monthly churn: LTV = ($30 × 80%) / 5% = $480.
For ecommerce: LTV = AOV × Gross Margin × Average Repeat Purchases.
The trap: most LTV calculations are based on tiny samples or extrapolation from new cohorts. Real LTV requires real cohorts that have been around long enough to see actual retention. If your business is 12 months old, your "LTV" is largely guesswork. Run with conservative assumptions until cohort data accumulates.
LTV/CAC and Payback Period
| LTV/CAC ratio | What it means | Action |
|---|---|---|
| Under 1:1 | Losing money on every customer | Stop spending; fix the model |
| 1:1 to 2:1 | Marginal — covering acquisition but little else | Improve retention or pricing before scaling |
| 3:1 (target) | Healthy — funds growth | Scale acquisition |
| 4:1+ | Strong — but check you're not underspending on growth | Test more acquisition channels |
| 10:1+ | Either misallocated or undervalued growth investment | Audit attribution; consider raising acquisition spend |
Payback period answers a different question: how long until a customer's gross profit covers their CAC?
Payback (months) = CAC / Monthly Gross Profit per CustomerBenchmarks by Business Model
| Model | Healthy LTV/CAC | Healthy payback | Notes |
|---|---|---|---|
| B2B SaaS | 3-5:1 | <12 months | Lower for enterprise (longer cycles) |
| Consumer subscription | 3:1 | <6 months | Churn destroys consumer-sub LTV faster |
| DTC ecommerce | 3-4:1 | 1-3 months | Low repeat rates mean fast payback matters |
| Marketplace | 3:1 on take-rate | 3-9 months | Track both sides; supply-side acquisition is often the constraint |
| Services / agency | 5:1+ | 1-2 contracts | High contribution margin per engagement; long sales cycle |
How to Use Unit Economics in Real Decisions
- Pricing. A 10% price increase usually doesn't lose 10% of customers — it almost always improves unit economics meaningfully. Test it.
- Channel evaluation. If a channel has a CAC that produces an LTV/CAC below 2:1, it's destroying value at scale even if volume looks good.
- Retention investments. A 1pp reduction in monthly churn raises subscription LTV by ~25% at typical ranges. Often the highest-ROI work in a business.
- Hiring. Hire the next salesperson when payback time will recoup their cost in under 12 months of attributed revenue.
- Fundraising. Investors model LTV/CAC and payback first. Going to market with weak unit economics significantly reduces valuation.
Red Flags
- LTV calculated from cohorts younger than your average customer lifetime.
- CAC that ignores fully-loaded marketing salaries.
- "Blended CAC" that mixes channels and hides bad ones.
- Contribution margin that excludes shipping, processing, or returns.
- Payback period longer than your runway.
Try It Yourself
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