J-Curve Payback Simulator
SaaS growth is expensive before it is profitable. This tool visualizes the "Cash Trough"-the period where you are cumulative negative on a customer-so you don't run out of money while growing.
Unit Economics
Cumulative Cash Flow
The path to profitability per customer
Break-Even Point
Month 18
Time to recover CAC
Lifetime Return
Recaport Cash Check
You are out of pocket for 18 months.Danger Zone. Your CAC is too high relative to your monthly profit. You are essentially lending money to your customers interest-free for over a year.
What is the "J-Curve"?
It's the shape of your cumulative cash flow per customer over time.
- Month 0: You spend $500 on ads (CAC). Your cash flow is -$500.
- Month 1-6: Customer pays you $50/mo. You are slowly climbing out of the hole.
- Month 10: You break even. The line crosses zero.
- Month 11+: Pure profit. The line goes up steeply (the J shape).
Why it kills startups
If your payback period is too long (e.g., 18 months), adding more customers actually burns more cash in the short term.
This creates the "Growth Paradox": The faster you grow, the faster you go bankrupt, unless you have the VC capital to bridge the trough.