Calculate Mortgage Payment

Here's a little diddy i wrote last night to calculate a mortgage payment. You can see the script in it's full glory on my Mortgage Calulator.

my %IN;
$IN{'AMOUNT'} = 100000;#as in $100,000 loan
$IN{'RATE'} = 6;##as in 6% interest
$IN{'YEARS'} = 30;## 30 years or 15 years etc
my $payment = &ComputePayment(%IN);
sub ComputePayment{
my %LOAN = @_;
my $years = $LOAN{'YEARS'};
my $interest = $LOAN{'RATE'};
my $principle = $LOAN{'AMOUNT'};
my $ttlmonths = $years*12;
my $iv = $interest/1200;
my $tmp = (1 + $iv) ** -$ttlmonths;
my $payment = 0;
if ($tmp < 1){
$payment = ($principle * $iv) / (1 - $tmp);
}else{
$payment = $principle / $ttlmonths;
}
return sprintf("%10.2f",$payment);
}########end SubRoutine
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Comment on Calculate Mortgage Payment Download Code

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Re: Calculate Mortgage Payment by Happy-the-monk (Canon) on Dec 14, 2005 at 10:43 UTC
The Mortgage Calculator dies with internal server error if you leave the "Years" field empty. You might want to do some error processing there. Alternatively, the way I think about paying mortgages I say I want to pay a monthly amount X, for how many years and months will I have to pay it off? You could offer that as an alternative, too. Cheers, Sören	[reply]
Re^2: Calculate Mortgage Payment by pajout (Curate) on Dec 14, 2005 at 11:52 UTC
And, just for enjoy, another quests are - calculate remaining payments when some payments are fixed (in time and in value, too) - calculate interest rate when all but non-equal payments are known, specially, when price is split into more than one payment... a little bit tricky, more than one interest rate can be the solution :)	[reply]