SaaS metrics
SaaS Unit Economics Calculator
See lifetime value, the LTV-to-CAC ratio, and payback from the same four inputs so the identities stay consistent.
Decision: Under these assumptions, what do LTV, LTV:CAC, and payback say?
This tool runs in your browser. FounderMage does not send the numbers you enter to our servers.
Result
Monthly contribution
Monthly contribution: $80.00
LTV
LTV: $2,000.00
LTV:CAC
LTV:CAC: 5
Payback
Payback: 5 months
How to read the result
These ratios describe the inputs you typed. They are not a claim that the business will retain customers or that CAC will stay constant.
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 × (margin ÷ 100). LTV is contribution ÷ (churn ÷ 100) when churn is between 0 and 100 exclusive; at 100% churn LTV is one month of contribution. LTV:CAC is LTV ÷ CAC. Payback is CAC ÷ contribution.
Assumptions
- Churn is a constant monthly rate.
- No expansion revenue unless included in ARPU.
Examples
Classic identity
$100 ARPU, 80% margin, 4% churn, $400 CAC: contribution $80, LTV $2,000, LTV:CAC 5.0, payback 5.0 months.
How to use this tool
- Enter ARPU, gross margin, monthly churn, and CAC.
- Read monthly contribution, LTV, LTV:CAC, and payback months.
Limitations
- Cohort curves, refunds, and contract terms are simplified away.
- Not investment advice.
Questions
- Why is LTV blank at 0% churn?
- The simple LTV formula divides contribution by churn. Zero churn would imply an unbounded lifetime, so the page refuses a fake number.
- What happens at 100% monthly churn?
- The customer lasts one period. LTV equals that month’s contribution.