Unit-economics formulas used here

The model assumes a constant monthly churn rate, flat revenue, flat margin, and no discount rate. It begins each month with the surviving cohort and applies churn between months. Real cohorts can expand, contract, reactivate, season, age, or change price.

Worked subscription unit example

The default customer produces $80 of monthly revenue at a 70 percent gross margin, or $56 of gross profit. Variable service and support consume $8, while payment, refund, and other variable cost consume $5. Contribution is therefore $43 per customer-month, a 53.75 percent contribution margin.

At 3 percent monthly churn, the reciprocal estimate gives a 33.33-month lifetime. Gross-profit LTV is $1,866.67. Removing $266.67 of lifetime service cost and $166.67 of other lifetime variable cost produces $1,433.33 of contribution LTV. CAC of $300 plus $50 onboarding creates a $350 acquisition investment and a 4.10x LTV:CAC ratio.

Gross-profit payback is 6.25 months, while contribution payback is 8.14 months because it recognizes more ongoing variable cost. A 1,000-customer cohort contributes about $438,826 during its first twelve modeled months and retains about 69.38 percent of its starting customers. After $350,000 of acquisition and onboarding spend, first-year cohort contribution is about $88,826.

Choose the unit before calculating economics

A unit should connect a revenue event to the costs and retention behavior management can change. Mixing per-order revenue with per-customer CAC creates a denominator error. Use one cohort, currency, period, and tax treatment throughout.

Build revenue and margin from governed definitions

Monthly revenue per customer should reconcile to recognized revenue or a clearly labeled operating measure. Bookings, billings, cash collected, GMV, ARR, MRR, and GAAP revenue differ. Taxes collected, pass-through amounts, credits, refunds, and reseller economics may require net treatment.

Gross margin should follow a consistent cost-of-revenue policy. Hosting, merchant fees, fulfillment, freight, customer support, implementation, depreciation, and partner share can sit in different lines across businesses. The calculator adds service and other variable cost below the entered gross margin so teams can reveal costs excluded from gross profit.

Do not publish a “contribution margin” that omits normal recurring cash costs without a clear definition. SEC staff guidance warns that labels and adjustments can make non-GAAP measures misleading. Internal discipline reduces that risk.

Calculate CAC with a complete acquisition pool

CAC can include paid media, agency fees, content, events, sales compensation, commissions, payroll taxes, benefits, software, data, travel, partners, free trials, discounts, creative production, and allocated management. Divide by acquired customers from the same time and scope.

Timing is difficult. Marketing spend can create customers later, and enterprise sales cycles cross quarters. Use cohorts, attribution windows, and lag analysis. Separate blended, paid, organic, new-logo, and expansion CAC without presenting one as another.

Onboarding is separated because it occurs after acquisition in many businesses. If onboarding is already inside COGS or CAC, enter zero to avoid double counting. Free hardware, implementation labor, data migration, and customer incentives should follow the actual cost policy.

Reciprocal churn is a shortcut, not a survival curve

The expression one divided by monthly churn is the expected lifetime for a constant geometric survival process. It is not the median lifetime, a contract term, or a guarantee. A 3 percent monthly churn rate does not mean each customer remains exactly 33.33 months.

Real churn varies by tenure, plan, segment, acquisition channel, and calendar. Early cohorts may have higher onboarding loss; mature cohorts may retain better. Expansion and contraction change revenue retention even when customer retention is stable.

Build a cohort survival table when history exists. Multiply each month’s expected active population by that month’s contribution, include expansion, and discount distant cash if material. The first-year cohort output already uses compounding rather than multiplying the starting contribution by twelve.

Payback and LTV:CAC answer different questions

Payback estimates how many months of contribution recover acquisition investment. It focuses on liquidity and speed. LTV:CAC compares an estimated lifetime contribution pool with acquisition investment. It is more sensitive to long-range retention assumptions.

A high LTV:CAC with a long payback can still strain cash. A short payback on a small market may not support growth. Review gross retention, NRR, contribution dollars, cohort size, working capital, acquisition capacity, and runway together.

The maximum-churn output solves the steady-state contribution formula for the entered target ratio. It is a boundary under current revenue, costs, and CAC, not a retention goal or prediction. If contribution is negative, lifetime scaling cannot repair the unit.

Use sensitivity before scaling acquisition

Stress average revenue, gross margin, service cost, refund rate, CAC, onboarding, and churn. A small churn change can produce a large LTV movement because churn is in the denominator. Set an evidence-based cap on forecast lifetime so sparse data do not justify unlimited spend.

Segment economics. Enterprise accounts may have high acquisition and implementation cost but durable contribution. Self-serve customers may pay back quickly yet churn rapidly. A blended ratio can hide a loss-making channel that grows fastest.

Scale only after measurement is stable, capacity exists, and cash can fund payback. Experiment incrementally, hold out controls where feasible, and compare predicted cohorts with realized contribution. Retire definitions that cannot be reconciled.

Accounting, tax, and disclosure boundaries

Unit economics do not replace GAAP revenue, gross profit, operating income, or cash flow. Public companies presenting non-GAAP measures must consider SEC rules and interpretations, including reconciliation and prominence requirements. KPIs also need clear definitions and disclosure of methodology changes when material.

Tax capitalization, inventory, startup cost, advertising, compensation, and revenue timing can differ from the operating model. IRS Publication 334 gives U.S. small-business context, but it does not endorse this LTV formula. Maintain invoices, payroll, campaign, cohort, and cost-allocation support.

It does not convert contribution LTV into taxable income, value a business, or determine deductible acquisition cost.

Unit-economics close checklist

1. Define the customer unit.
2. Freeze the cohort period.
3. Reconcile revenue scope.
4. Document gross-margin costs.
5. Add omitted variable service cost.
6. Reconcile acquisition spend.
7. Apply a consistent attribution lag.
8. Separate onboarding without duplication.
9. Measure cohort churn.
10. Compare payback and lifetime.
11. Stress every major driver.
12. Archive definition changes.

Frequently asked questions

References

• SEC Commission Guidance on KPIs and metrics in MD&A
• SEC Compliance and Disclosure Interpretations, non-GAAP financial measures
• U.S. Small Business Administration break-even point calculator and cost guidance
• IRS Publication 334, Tax Guide for Small Business