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Engineering ToolBox > Net Present Worth - NPW - of a Stream of Payments
The present value of a stream of payments

can be calculated with the discounting factor
NPW = F0 / (1 + i)0 + F1 / (1 + i)1 + F2 /(1 + i)2 +�.... + Fn /(1 + i)n� (1)
where
NPW = present worth or value
F = future cash flow
i = discount rate
The present worth by investing 1000 today receiving 250 every year in 5 years at an interest or discount rate of 10%, can be calculated
NPW = - 1000 / (1 + 0.1)0 + 250 / (1 + 0.1)1 + 250 /(1 + 0.1)2
����������� + 250 /(1 + 0.1)3 + 250 /(1 + 0.1)4 + 250 /(1 + 0.1)5
��� = -52.3
PV is negative - and the investment should be avoided.
A more flexible Net Present Value and Internal Rate Calculator in Excel spreadsheet format is available here!