Customer economics
CAC Payback Calculator
Put CAC against monthly contribution and see how long recovery takes, including a simple retained-contribution shock.
Decision: How long does it take this acquisition cost to pay back?
This tool runs in your browser. FounderMage does not send the numbers you enter to our servers.
Result
Monthly contribution
Monthly contribution: $60.00
Payback months
Payback months: 6.7 months
Payback after churn shock
Payback after churn shock: 7 months
How to read the result
A shorter payback means the contribution you entered recovers the CAC you entered faster. It is not a verdict to spend more on ads.
Calculated facts
Totals and thresholds come only from the values on this page. They describe the math, not what you should do.
Still a judgment call
Risk, timing, customers, and judgment stay outside the calculator. A stronger number can still be the wrong path.
Methodology
Monthly contribution is ARPU × (gross margin ÷ 100). Payback months are CAC ÷ contribution when contribution is positive. The churn case uses contribution × (1 − churn).
Assumptions
- Contribution repeats each month until payback.
- Churn is a simple monthly haircut, not a full retention curve.
Examples
Simple payback
$400 CAC, $80 monthly revenue, 75% margin is $60 contribution and 6.67 months to recover CAC.
How to use this tool
- Enter CAC, monthly revenue per customer, and gross margin percent.
- Optionally set monthly churn to compare a retained-contribution case.
- Read base payback months and the churn-adjusted case.
Limitations
- Refunds, payment delays, and multi-product attach are omitted.
- Not marketing or investment advice.
Questions
- Do you use a typical CAC?
- No. Typical CAC figures are not certified here. Enter the acquisition cost you actually incur or assume.
- What does the churn field change?
- It reduces monthly contribution by the retained fraction so you can see payback if that much revenue is lost each month.