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Conference nyoss1::market_investing

Title:Market Investing
Moderator:2155::michaud
Created:Thu Jan 23 1992
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1060
Total number of notes:10477

459.0. "Amortization formula?" by MRSVAX::TSMITH (That rabbit's dynamite...) Fri Apr 23 1993 17:21

I've poked around this conference a couple of times and haven't found a formula
for calculating the amortization of a loan.  Does anyone know what the exact
formula the banks use?  Is this the correct conference for this question?

I'm looking to write a program which would go beyond the standard amortization
programs and optionally show what happens to the principle and interest if you
choose to prepay the principle as you go.

Any help would be appreciated.

Thanks,
/T
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459.1SOLVIT::REDZIN::DCOXFri Apr 23 1993 17:518
    I presume (which gets me into trouble form time to time) that you are
    looking for the standard Annuity formula; that is, for P=principal,
    n=number of periods, PMT = payment per period, and i = interest rate
    per period:
    
    PMT=P/((1-((1+i)^n))/i)
    
    Dave
459.2normal amortizationSLOAN::HOMMon Apr 26 1993 09:087
For a fixed rate mortage,  the interest paid for a given month 
is just the balance x annual interest / 12.

You can verify this requesting this information from your
bank. Some banks print this information on the monthly statement.

Gim
459.3It's already out thereKALI::PLOUFFLifestyles of the unrich and anonymousMon Apr 26 1993 10:1113
    There are several public domain programs for the IBM PC, UNIX systems,
    and various personal computers which do exactly what the basenoter
    desires.  A little poking around might save considerable time if the
    results are more important than the method.
    
    It's been my experience, though, that calculations done at home never
    match the bank's numbers exactly because of partial month payment at
    the beginning of the loan term, and because the bank probably uses a
    different calculation method than the simple formula for whatever
    (historic?) reason.  However, for results within $10-50 the PD software
    does just fine.
    
    Wes
459.4Thanks!MRSVAX::TSMITHThat rabbit's dynamite...Mon Apr 26 1993 11:135
Thanks to everyone.  That's what I needed to know.  I guess I'll ask the bank
for an amortized schedule so I can see how close mine comes to it.

Cheers,
/T
459.5OpenVMS pgm availableTOOK::FAULDSFri May 07 1993 16:518
    For the VAX processor family...check the Toolshed.
    
    METOO::TOOLS$LIBRARY:MORTGAGE.LIS  (also .KIT)
    
    ABSTRACTS.LIS in the same location lists ALL the tools available in the
    toolshed and a synopsis of each tool.
    
    -Rob