How to use this calculator
Enter an initial negative outlay and subsequent signed period-end cash flows. Select discounted payback to enter a per-period discount rate.
Formula and method
Simple cumulative = sum Cₜ. Discounted cumulative = sum Cₜ/(1+r)ᵗ. First crossing is interpolated as prior full periods + unrecovered amount / crossing-period inflow.
Worked example
−1,000 now, then 400 in each of three years: simple payback is 2.5 years; with 450 in each year and a 10% discount rate, discounted payback is about 2.65 years.
Assumptions and supported scope
Equal periods; period 0 is now. Discount rate greater than −100%. The within-period fraction is an approximation; later reversals are possible. No recommendation is implied.
Method references
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