Re: mortgage calculator

At 17:49 5-3-03, you wrote:

I'd like to add a mortgage calculator to a client's site. I've been unable to find the formula.

Well the calculation depends on the companies policy of course. 1. Normal rent calculation would go like this: where i = interest or rent over a certain the period of time (

        usually between 0 and 1 (1=100%). With 3.5% interest, i is 3.5/100=0.035

n = the amount of timeperiods that passed $ = pack of money , and $(0) is heap at start, $(n) is at end of n timeperiods $(n)= $(0) * (1+i)^n (x raised-to-the-power-of y is sometimes written as x^y, sometimes as x**y (Perl)) in PHP

        $startsum=$_POST['startsum'];
        $interest=$_POST['interest'];
        $timeperiods=$_POST['timeperiods'];

$endsum = $startsum * pow(1+$interest/100,$timeperiods); With a 3% year-rent in 5 years $10 grows to $(n) = 10 * 1.03^5 2. Mortgage calculation Well how do they pay back? You can have them pay a fixed part of the loan plus the interest of the month, here called an annuiteiten-hypotheek Then every month you pay

($in_this_month *interest)      +     (1/$totalmonths * $startsum )

$in_this_month is probably $n=thismonths number so the monthly payment would look something like

((1 - $n/$totalmonths) * $startsum ) +     (1/$totalmonths * $startsum )

I suppose you can simplify this if you are a mathematician. If you are a bloody consultant you should have learned these formulas once up on a time. You can loop through $n of course to make a nice list.

In searching php.net, I found a discussion from back in 2000 related to some buggy code. My web search hasn't produced anything other than realtor and mortgage companies and a perl script site. I'm not familiar with perl and would prefer avoiding it until my knowledge improves. There were corrections for a java script somewhere, but I'm beginning to think it is down. Some things seem so obvious that you just don't think you need to bookmark! So why can't I remember... Perl is not that hard to translate to PHP if it is clear what every variable means.