Unit economics describe how much a business earns and spends on each unit it sells — usually a customer, subscription, or transaction — after the costs tied directly to delivering that unit.

How it works

Start by defining the unit. A B2B SaaS company might use one customer account; a marketplace uses one completed order; a fintech app might use one active user per month. Revenue per unit is straightforward: average contract value divided by customers, or take rate times order value. Direct costs include hosting, payment fees, customer support tied to delivery, and cost of goods sold. Gross profit per unit is revenue minus those direct costs.

Then layer acquisition and retention. CAC (customer acquisition cost) divided by gross profit per month gives payback period — how long until that customer repays sales and marketing. LTV estimates total gross profit over the customer lifetime. Healthy models show LTV meaningfully above CAC with payback inside a reasonable window for the category. Example: $100/month subscription, 75% gross margin, $600 CAC → $75 gross profit per month → eight-month payback if churn is low.

Investors stress-test assumptions: what if CAC rises when you leave early channels, or churn spikes after discounts end?

Why it matters

• Founders: Unit economics tell you whether to pour fuel on growth or fix pricing, onboarding, or product cost first. Board decks that show improving contribution margin per cohort build credibility.
• Investors: Venture dollars fund scale when each incremental unit gets cheaper to serve or more valuable to keep — not when losses widen with every sale.

Common mistake

Reporting company-wide gross margin while ignoring fully loaded CAC, or blending enterprise and self-serve customers into one misleading “average unit.”

Related ideas

See also CAC, LTV, gross margin, contribution margin, and cohort analysis.