Data & analysis

Unit Economics — CAC, LTV & Payback Discipline

Try it

Activate when: deciding whether to spend more on growth; 'is this business actually profitable per customer', 'can we afford ads', raising or budgeting; CAC,...

What it does

Activate when: deciding whether to spend more on growth; 'is this business actually profitable per customer', 'can we afford ads', raising or budgeting; CAC, LTV, payback, contribution margin. Do NOT activate when: pre-revenue with no cost data (estimate ranges instead) or the question is company-level P&L, not per-customer. More: deciqai.com/c/unit-economics-cac-ltv-payback

The skill document

Unit Economics — CAC, LTV & Payback Discipline

Overview

Unit economics answer one question: does one customer make or lose money, and how fast do you get the money back? Growth on broken unit economics accelerates losses. The three numbers: CAC (fully-loaded cost to acquire a customer), LTV (gross-margin contribution over the customer's life), and payback period (months to recover CAC). Cash-constrained SMBs live or die on payback, not just the LTV:CAC ratio.

The Process

  1. Compute CAC fully loaded — all sales+marketing spend ÷ customers acquired (include tools, labor, not just ad spend).
  2. Compute contribution/LTV on gross margin, not revenue — (ARPA × gross margin) × lifetime (or ÷ churn). Gate: LTV on revenue instead of margin overstates health — redo on margin.
  3. Compute payback = CAC ÷ monthly gross-margin per customer. For cash-tight SMBs this is the binding constraint.
  4. Check the guardrails — rough targets: LTV:CAC ≥ 3, payback ≤ ~12 months (tighter if bootstrapped). Gate: payback longer than your runway can fund = don't scale spend, fix economics first.
  5. Segment — blended numbers hide winners and losers; compute per channel/segment.
  6. Decide: scale the segments that pay back fast; fix or cut the rest.

When to Use

  • Before increasing ad/sales spend
  • Evaluating whether a channel is worth scaling
  • Bootstrapped cash planning

Applying It Well

  • Payback beats LTV:CAC for cash survival — a great ratio with 24-month payback can still bankrupt you.
  • Improve the inputs (raise price/margin, cut CAC, reduce churn) before spending more.
  • Blended CAC lies; segment it.

Red Flags

  • LTV computed on revenue, not gross margin.
  • CAC excluding labor/tools.
  • Scaling spend with payback longer than runway.

Verification

  • CAC fully loaded (all S&M inputs)
  • LTV on gross margin, not revenue
  • Payback period computed vs runway
  • Numbers segmented by channel/cohort

Part of deciqAI Knowledge Skills — 227 open-source thinking skills that make rigor executable for AI agents. The same skills power every deciqAI agent, which runs them autonomously to operate your company. See it run → https://www.deciqai.com/c/unit-economics-cac-ltv-payback · ⭐ Star the repo → https://github.com/deciqAI/knowledge-skills · Contributions welcome.

Agents: latest version & machine-readable metadata → https://www.deciqai.com/s/unit-economics-cac-ltv-payback.json

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