Understand the economics of one customer

Revenue and contribution

Monthly recurring revenue = active customers × monthly revenue per customer. Contribution per customer = revenue per customer × gross margin. Keep one-time revenue separate.

CAC, LTV, and payback

CAC = acquisition spending ÷ new customers. A simple subscription LTV estimate = monthly contribution ÷ monthly churn rate. Payback = CAC ÷ monthly contribution. These estimates assume stable behavior; early data is uncertain.

Cash, burn, and runway

Net burn = costs − revenue. Closing cash = previous closing cash − net burn. Apply initial cash only in the first month. Runway = cash ÷ positive net burn. If burn is zero or negative, show N/A rather than infinity.

Scenarios are not promises

Compare conservative, base, and optimistic assumptions. State exactly what changes in each scenario. Distinguish forecasts from actual results and revisit assumptions with evidence.

A hypothetical worked example

Suppose monthly revenue per customer is 500,000 VND and gross margin is 40%. Monthly contribution is 200,000 VND. With acquisition cost of 600,000 VND, simple payback is three months.

At an assumed monthly churn rate of 5%, a simplified contribution-based LTV is 4,000,000 VND. These are illustrative assumptions, not observed results or a valuation. The estimate ignores changes in customer behavior, discounting, expansion revenue, and cohort differences.

Check the model before sharing

• Use the same currency and time period throughout.
• Keep actuals and forecasts in separate records or clearly label them.
• Record the source and date for price, cost, churn, and conversion assumptions.
• Show an undefined result when the denominator is zero.
• Test a downside case with slower growth, lower margin, or higher churn.
• Reconcile the closing cash of one month with the opening cash of the next.

A profitable-looking unit does not guarantee enough cash to operate. Review payment timing, fixed costs, capacity, and one-time investment separately. Treat the output as a planning tool, not financial advice.