PMT() & DATEDIF() Problems

[Beachcomber]

Hi, I'm making a simple Loan calculator to determine my monthly payments using the PMT() function.

PMT(rate,nper,pv,fv,type)

My inputs are as follows:

RATE (Interest Rate): 9%
NPER (Number periods): DATEDIF(TODAY(),6/1/2006,"m") [Note: The second date is actually in a seperate cell, and I reference that cell in the formula]
PV (Present Value): $50000
FV (Future Value):
Type: 1 (Payments made at beginning of each period)

I'm trying to integrate these inputs into my function in the following manner:

=PMT(.09/12,DATEDIF(TODAY(),6/1/2006,"m"),50000,0,1)

In order to determine my monthly payments. I'm making the number of periods the difference between a future date (6/1/2006) and today's date (11/9/05).

However, the Type is 1, meaning that I make my payments at the beginning of each much eg. March 1, etc.

When I'm using DATEDIF() to determine the number of whole months between two dates, it does not always return the proper number of months for the NPER(). For example, taking todays date (11/09/05) and finding the number of months between it and 6/1/2006, returns a value of 6 months.

However, there are actually 7 payment periods since June 1, 2006 is also a payment period and the date the loan is terminated. I know I could simply add +1 to my DATEDIF() Formula to get the proper number of months, but I want my formula to work for any date, even if the current date is the first of a month.

Any suggestions or strategies for improving my formula? Is DATEDIF() the best way to find the number of months for my NPER in the PMT() Function? Thank you so much - this problem has been very stressful.

 

[fairwinds]

Hi,

If your date is in A1, try:

=PMT(0.09/12,DATEDIF(TODAY(),EOMONTH(A1,0)+1,"M"),50000,0,1)