7-3-1

Compound Interest

7-3 Compound Interest

This calculator uses the following standard formulas to calculate compound interest.

uFormula I

PV + PMT

(1 + i S)[(1+ i)n –1]

1

= 0

i =

I %

 

+ FV

 

 

i(1 + i)n(1 + i)n

 

 

 

 

100

Here:

PV = – (PMT α + FV β )

FV = – PMT α + PV

β

PMT = –PV + FV β

α

 

{(1+ i S ) PMT FVi }

log

(1+ i S ) PMT + PVi

n=

 

 

 

 

log(1 + i)

α

=

 

(1 + i S)[(1 + i)n –1]

 

 

 

 

 

i(1+ i)n

 

 

 

 

β

1

 

=

 

 

 

(1+ i)n

 

 

PV : present value

FV : future value

PMT : payment

n: number of compound periods

I% : annual interest rate

i is calculated using Newton’s Method.

S = 0 assumed for end of term

S = 1 assumed for beginning of term

F(i) = Formula I

 

 

F(i)' =

PMT

[

(1 + i S)[1 – (1 + i)n]

+ (1 + i S)[n(1 + i)n–1]

i

 

 

 

i

+S [1 – (1 + i)n]]nFV(1 + i)n–1uFormula II (I% = 0)

PV + PMT n + FV = 0

Here:

PV = – (PMT n + FV )

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