Discount a stream of cash flows to compute Net Present Value, Internal Rate of Return, modified IRR, discounted & undiscounted payback, and the profitability index. Cash flows can be irregular and may switch sign multiple times. The cumulative-flow chart shows when the project turns the corner. Everything runs in your browser.
| t | Cash flow | Discount factor | Discounted CF | Cumulative | Disc. cumulative |
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NPV discounts each future cash flow back to period 0 at rate r and sums them. NPV > 0 means the project beats the discount rate; NPV < 0 means it doesn't.
IRR is the discount rate that makes NPV exactly zero. It's solved here with Newton's method (with bisection fallback). A series with multiple sign changes can have multiple IRRs — only the first real root in a sensible range is reported, so prefer NPV when in doubt.
MIRR assumes outflows are financed at the finance rate and inflows are reinvested at the reinvest rate, removing the unrealistic "reinvest at the IRR" assumption baked into plain IRR. MIRR = (FVinflows / |PVoutflows|)1/n − 1.
Payback is the period number at which cumulative cash flow crosses zero, interpolated linearly within the period. The discounted version uses discounted cash flows. "—" means it never crosses.
Profitability index = PV of inflows divided by the absolute value of PV of outflows. PI > 1 is the same go-ahead signal as NPV > 0, but lets you rank projects of different sizes by efficiency.