finance
Unit Economics
Revenue and cost per single unit (customer, transaction, project). The atom of business viability.
Definition
Unit economics is the profitability of a single unit - one customer, one transaction, one project. The standard B2B service framing: LTV (lifetime value per customer) vs CAC (cost to acquire). When LTV/CAC > 3 and CAC payback < 12 months, the business can scale profitably. When LTV/CAC < 1, every new customer destroys value. Unit economics is the most-overlooked diagnostic in struggling businesses - founders see top-line growth and miss that each new customer is unprofitable.
The five core unit economics metrics
Customer Acquisition Cost (CAC): total sales and marketing spend divided by new customers acquired. Lifetime Value (LTV): gross profit per customer over their full retention period. LTV to CAC ratio: target above 3 for healthy. CAC Payback Period: months until cumulative gross profit equals CAC; target under 12 months for SMB SaaS, under 24 for enterprise. Gross Margin per customer: revenue per customer minus direct delivery cost. These five together describe whether each new customer creates or destroys value. Reporting them at company level, then by segment and by channel, is the unit economics dashboard every US SaaS or service business should run weekly.
Why unit economics fail at scale
A common pattern in US startups: unit economics look great at 100 customers because the highest-intent, lowest-CAC customers come first. As acquisition scales to 1000 or 10000 customers, blended CAC rises (saturating high-intent channels), LTV may drop (less ideal-fit customers), and the LTV to CAC ratio that was 5:1 compresses to 2:1. Founders who do not stress-test unit economics for the next 10x of growth get caught when growth slows and they cannot raise the next round. Always project unit economics for the target customer cohort 12 to 24 months out, not just trailing 6 months.
Segment-level unit economics
Blended unit economics hide profitable and unprofitable segments. A typical US B2B SaaS has SMB unit economics that are marginal (LTV:CAC 1.5 to 3:1, payback 12 to 24 months) and enterprise unit economics that are excellent (LTV:CAC 5 to 10:1, payback 12 to 18 months). Aggregating them produces a healthy-looking blended number that masks the SMB drag. The right move is to either fix SMB economics (raise prices, lower CAC) or shift go-to-market resources toward enterprise. Always run unit economics by segment, by acquisition channel, by industry vertical, and by deal size.
When unit economics matter most
Three decision points. One, before scaling paid acquisition: if LTV:CAC is below 3:1, more spend amplifies losses. Two, before a fundraise: investors will dig into unit economics in due diligence; weak numbers kill rounds. Three, before pricing changes: model whether a 10 percent price increase improves LTV:CAC even with elevated churn. The rule: do not scale anything (hiring, marketing, product investment) until unit economics support the math. Many US startups that died in 2022 to 2023 had revenue growth but broken unit economics; the correction came when capital tightened.
FAQ
Should unit economics use gross profit or revenue?
Always gross profit, not revenue. LTV calculated on revenue creates LTV:CAC ratios that look healthy until you realize half the revenue is delivery cost. A 10000 LTV at 30 percent gross margin is really 3000 LTV. If your CAC is 2000, the LTV:CAC on revenue looks 5:1 (great), but on gross profit it is 1.5:1 (marginal). Sophisticated US investors always compute LTV on gross profit; founders who do not have to walk it back during diligence.
How does cohort analysis fit into unit economics?
Cohort analysis groups customers by signup month and tracks them over time. Cohort retention curves show actual churn behavior, which produces the most accurate LTV. Cohort revenue curves show expansion behavior (NRR). Cohort gross margin curves catch delivery cost drift. Without cohorts, unit economics are an average that hides the truth. Tools like Mixpanel, Amplitude, ChartMogul, and Looker run cohort analysis automatically once data is connected.
What is contribution margin in unit economics?
Contribution margin per customer is revenue per customer minus variable cost per customer (COGS plus variable selling cost). It is the marginal profit each customer adds before covering fixed overhead. For SaaS, contribution margin per customer is often 70 to 85 percent. For services, 30 to 60 percent depending on labor intensity. Healthy unit economics require positive contribution margin; if a customer does not cover their own variable cost, scaling makes things worse.
How do unit economics differ for transactional versus subscription businesses?
Subscription unit economics use LTV based on retention and recurring revenue. Transactional unit economics use repeat purchase rate, average order value, and order economics. A US e-commerce business calculates LTV as average order value times gross margin times average lifetime orders. The metric framework is similar but the inputs differ. Investors and operators in transactional businesses watch repeat purchase rate (rate of return customers) the way SaaS watches NRR.
Are unit economics relevant for service businesses without recurring revenue?
Yes, with adaptation. Project-based service businesses calculate unit economics per project: revenue per project, COGS per project, gross margin per project. CAC translates to business development cost per won project. LTV maps to expected repeat business value from that client. While the metrics are noisier than subscription, they still answer the key question: does each engagement create or destroy value?
In your business
- →Calculate unit economics before scaling acquisition spend - growth amplifies whatever the unit math is
- →LTV/CAC ratio above 3 is healthy; CAC payback under 12 months is healthy
- →Decompose by segment - SMB and enterprise often have wildly different unit economics