This estimator calculates customer acquisition payback time for a pre-seed business by dividing acquisition cost per customer by monthly gross profit generated by that customer. It provides a simple answer to how many months of contribution are needed to recover sales and marketing spend.
Founders can use the estimate to compare channels, test pricing, and understand whether available runway supports the acquisition strategy. The model assumes stable monthly revenue and margin and does not discount future cash flows or include ongoing account-management costs unless those costs are reflected in gross margin.
1. Enter acquisition cost
Use fully loaded sales and marketing cost per newly acquired customer.
2. Enter monthly customer revenue
Use recurring revenue expected from one average active customer.
3. Set gross margin
Enter the portion of revenue left after direct delivery costs.
4. Review payback time
Compare the result with expected retention and available cash runway.
Monthly gross profit per customer = Monthly revenue × Gross margin CAC payback months = Customer acquisition cost ÷ Monthly gross profit per customer
The method assumes contribution is earned evenly each month and excludes the time value of money.
The result estimates how long one average customer must remain active to recover acquisition spending.
Use channel-specific CAC and customer economics when performance varies materially.
Given: CAC = $600, monthly revenue = $120, gross margin = 80%.
Calculation: Monthly gross profit = $120 × 0.80 = $96. Payback = $600 ÷ $96 = 6.25 months.
Result: Acquisition spend is recovered in about 6.25 months.
Include it when you want a fully loaded economic view, especially if founder-led sales will later require paid staff.
Gross profit better represents the contribution available to repay acquisition cost.
This simplified model assumes a constant amount. A cohort cash-flow model is better for ramping or usage-based revenue.
Yes, but that indicates the modeled customer may churn before acquisition cost is recovered.
Payback focuses on recovery speed, while LTV:CAC compares total modeled customer value with acquisition cost.