how do i calculate the discounted payback period 
the discounted payback period is more accurate than the standard payback period but more difficult to calculate the first step is to estimate the expected annual cash flows from the investment as well as the discount rate the amount of value an amount of cash loses with each successive year due to inflation and the diminishing time value of money this is used to calculate the present value of each instance of cash flow and the discount payback period is the number of years it takes for the discounted cash flows to exceed the initial investment 