#!/usr/local/bin/perl $args = $ENV{'QUERY_STRING'}; print "Content-type: text/html\n\n"; if (length($args) < 3) { print <Future Value/Annuity Calculation

Future Value/Annuity Calculation

Since the mortgage calcuator is so popular, I put together a form that does another calculation I find important, finding out how much to put away tax deferred to get a certain amount of money in the future, and how much you could expect to draw out of that money.

FullForm } else { print "Future Estimations\n"; print "

Future Estimations

\n"; # Let's do the calculations! @va = split("&",$args); for ($i=0; $i<7; $i++) { @va[$i] = substr(@va[$i],5); } ($abal,$pymt,$time,$intr,$infl,$raiz,$wdrw) = @va; print "

Inputs

\n"; print "

Beginning Balance of Account	\$ $abal\n"; print "
Initial monthly contribution	\$ $pymt\n"; print "
Time until retirement	$time years\n"; print "
Estimated annual yield	$intr % \n"; print "
Estimated annual inflation	$infl % \n"; print "
Estimated annual contribution increase	$raiz % \n"; print "
Desired monthly withdrawal	\$ $wdrw (current dollars)\n"; print "

\n"; $intr = $intr/1200; $raiz = $raiz/100; $infl = $infl/100; $adj = 1; print "\n"; print "

Year	Monthly Contrib	Actual Balance"; print "	Current Dollar Balance\n"; for ($i=0; $i<$time; $i++) { for ($j=0; $j<12; $j++) { $abal = $abal * (1 + $intr) + $pymt; } $pymt = $pymt * (1 + $raiz); $adj = $adj/(1 + $infl); $pbal = $abal * $adj; printf("
%2d	\$ %9.2f	\$ %11.2f	\$ %11.2f\n", $i+1,$pymt,$abal,$pbal); } $awdr = $wdrw/$adj; print "

At this time:

\n"; printf("

Your last monthly contribution was : \$ %9.2f\n",$pymt); printf("

Your current required withdrawal is : \$ %9.2f\n",$awdr); print "

Let's start taking money out and see how long it lasts

\n"; if ($intr > 6/1200) { print "

Lets say you will NOT be able to maintain annual interest of"; print "more than 6% once you start taking out money\n"; print "

I am taking your yield down to 6.0%\n"; $intr = 6/1200; } print "\n"; $obal = $abal; print "

Year	Balance	Annual Withdrawal\n"; while($abal > 0) { $yr++; $annw = 0; for ($j=0; $j<12; $j++) { if ($abal * (1 + $intr) > $awdr) { $abal = $abal * (1 + $intr) - $awdr; $annw = $annw + $awdr; } else { $annw = $annw + $abal; $abal = 0; $j = 12; } } printf("
%2d	\$ %9.2f	\$ %9.2f\n", $yr, $abal, $annw); $awdr = $awdr * (1 + $infl); if ($abal > ($obal * (1 + $infl))) { print "

Congratulations! You are set for life!

\n"; print "Your balance is earning more than you are taking out\n"; $abal = 0; } $obal = $abal } print "\n"; }

	Beginning Balance of Account
	Monthly contribution
	Years until retirement
	Estimated annual yield (%)
	Estimated annual inflation (%)
	Estimated annual contribution increase(%)
	Desired future monthly withdrawal amount (current dollars)