CUMPRINC / CUMIPMT Math

[T Rex]

Can anyone tell me the math behind these Excel functions using the
parameters listed? I am writing some software and I am unable to use
Excel to calculate these but I still need the same result.

Thanks for the help.

John

CUMPRINC(rate,nper,pv,start_period,end_period,type) Returns the cumulative
principal paid on a loan between start_period and end_period.

Rate is the interest rate.
Nper is the total number of payment periods.
Pv is the present value.
Start_period is the first period in the calculation.
Payment periods are numbered beginning with 1.
End_period is the last period in the calculation.
Type is the timing of the payment.
Type Timing0
(zero)Payment at the end of the period
1 Payment at the beginning of the period

and

CUMIPMT(rate,nper,pv,start_period,end_period,type) Returns the cumulative
interest paid on a loan between start_period and end_period.

CUMIPMT(rate,nper,pv,start_period,end_period,type)

Rate is the interest rate.
Nper is the total number of payment periods.
Pv is the present value.
Start_period is the first period in the calculation.
Payment periods are numbered beginning with 1.
End_period is the last period in the calculation.
Type is the timing of the payment.
Type Timing
0 (zero) Payment at the end of the period
1 Payment at the beginning of the period

 

[Jerry W. Lewis]

Help for PV gives the basic formula underlying Excel's financial functions.

Jerry