From: glyn <glyn@8kb.co.uk>
Date: Thu, 5 Jun 2014 16:25:39 +0000 (+0100)
Subject: Initial commit
X-Git-Url: https://git.8kb.co.uk/?a=commitdiff_plain;h=8bb71868a84b00332b067afc5ab660fd7e692a80;p=playtime%2Fmortgage_calculator

Initial commit
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8bb71868a84b00332b067afc5ab660fd7e692a80
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+.DS_Store
+Thumb.db
diff --git a/README.md b/README.md
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+# Mortgage cost calculator
+
+A few years back whilst buying my first house I was looking for some sort of 
+mortgage calculator to churn out the basics of what interest and capital I'd be 
+paying off over the term of different mortgage deals available to me.
+
+I couldn't find anything, and seeing as the word "mortgage" in French pretty 
+much translates to "death pledge" I though it was a good idea to get it right!
+
+So, fed up of getting the calculator out again and again I mocked up this quick 
+and dirty perl script, which is essentially for just fixed interest rate deals 
+but can be used to estimate tracker types too.
+
+##Parameters are:
+
+mortgage_value *-m*		Value of the mortgage (i.e. Property value minus Deposit)
+arrangement_fee *-a*		Any arrangement fee on the initial mortgage
+interest_rate *-i*		The rate in percent of the initial mortgage deal
+interest_rate_term *-it*	The term for the initial interest rate
+term *-t*			The total term of the mortgage (defaults to 25 years)
+interest_rate_increase *-ii*	A yearly increace for the interest rate outside of the initial fixed term
+cap_rate_increase *-ic*		Cap the yearly interest increase at a particular value
+monthly_overpayment *-o*	The value of any regular monthly overpayments you intend to make
+monthly_payment *-p*		An amount you decide you want to pay off each month (calculated from mortgage value, rate and term otherwise)
+
+##Example usage
+
+The simplest input for the script is just a mortgage value and an interest rate; the
+script then defaults to a 25 year term at the same fixed rate.  So if I wanted a house
+costing £105k with a £5k deposit with a fixed 3.2% rate (obviously this isn't much use 
+but just for illustration):
+
+<pre>
+$ ./mcalc.pl -m=100000 -i=3.2
+
+Mortgage value: 100000
+Arrangement fee added on: 0
+Term: 25 year(s)
+Interest rate: 3.2% (Monthly rate = 0.00266666666666667%)
+Interest rate term: 1 years
+Initial monthly payment: 484.68
+After initial term rate jumps by: 0
+---------------------------------------
+Total mortgage value: 100000
+---------------------------------------
+
+End of year 1    Mortgage: 97345.14   Total paid: 5816.15    Total interest: 3154.21     (Rate 3.2%, Monthly Payment 484.68)
+End of year 2    Mortgage: 94433.05   Total paid: 11800.81   Total interest: 6219.02     (Rate 3.2%, Monthly Payment 498.72)
+End of year 3    Mortgage: 91426.40   Total paid: 17785.48   Total interest: 9189.02     (Rate 3.2%, Monthly Payment 498.72)
+End of year 4    Mortgage: 88322.11   Total paid: 23770.15   Total interest: 12061.12    (Rate 3.2%, Monthly Payment 498.72)
+End of year 5    Mortgage: 85117.02   Total paid: 29754.81   Total interest: 14832.14    (Rate 3.2%, Monthly Payment 498.72)
+End of year 6    Mortgage: 81807.84   Total paid: 35739.48   Total interest: 17498.81    (Rate 3.2%, Monthly Payment 498.72)
+End of year 7    Mortgage: 78391.21   Total paid: 41724.14   Total interest: 20057.73    (Rate 3.2%, Monthly Payment 498.72)
+End of year 8    Mortgage: 74863.62   Total paid: 47708.81   Total interest: 22505.40    (Rate 3.2%, Monthly Payment 498.72)
+End of year 9    Mortgage: 71221.48   Total paid: 53693.47   Total interest: 24838.21    (Rate 3.2%, Monthly Payment 498.72)
+End of year 10   Mortgage: 67461.07   Total paid: 59678.14   Total interest: 27052.44    (Rate 3.2%, Monthly Payment 498.72)
+End of year 11   Mortgage: 63578.54   Total paid: 65662.81   Total interest: 29144.22    (Rate 3.2%, Monthly Payment 498.72)
+End of year 12   Mortgage: 59569.94   Total paid: 71647.47   Total interest: 31109.59    (Rate 3.2%, Monthly Payment 498.72)
+End of year 13   Mortgage: 55431.16   Total paid: 77632.14   Total interest: 32944.44    (Rate 3.2%, Monthly Payment 498.72)
+End of year 14   Mortgage: 51157.97   Total paid: 83616.80   Total interest: 34644.53    (Rate 3.2%, Monthly Payment 498.72)
+End of year 15   Mortgage: 46746.03   Total paid: 89601.47   Total interest: 36205.49    (Rate 3.2%, Monthly Payment 498.72)
+End of year 16   Mortgage: 42190.81   Total paid: 95586.13   Total interest: 37622.79    (Rate 3.2%, Monthly Payment 498.72)
+End of year 17   Mortgage: 37487.67   Total paid: 101570.80  Total interest: 38891.77    (Rate 3.2%, Monthly Payment 498.72)
+End of year 18   Mortgage: 32631.80   Total paid: 107555.47  Total interest: 40007.62    (Rate 3.2%, Monthly Payment 498.72)
+End of year 19   Mortgage: 27618.25   Total paid: 113540.13  Total interest: 40965.36    (Rate 3.2%, Monthly Payment 498.72)
+End of year 20   Mortgage: 22441.88   Total paid: 119524.80  Total interest: 41759.86    (Rate 3.2%, Monthly Payment 498.72)
+End of year 21   Mortgage: 17097.42   Total paid: 125509.46  Total interest: 42385.81    (Rate 3.2%, Monthly Payment 498.72)
+End of year 22   Mortgage: 11579.41   Total paid: 131494.13  Total interest: 42837.75    (Rate 3.2%, Monthly Payment 498.72)
+End of year 23   Mortgage: 5882.21    Total paid: 137478.80  Total interest: 43110.02    (Rate 3.2%, Monthly Payment 498.72)
+End of year 24   Mortgage: -0.00      Total paid: 143463.46  Total interest: 43196.79    (Rate 3.2%, Monthly Payment 498.72)
+Paid off in month 12 of year 24
+
+</pre>
+
+A more useful example would be to also specify all the other usual variables, 
+so lets also specify a mortgage term of 20 years, with an initial mortgage deal
+of 3.2% fixed for 3 years with a £995 arrangement fee, after the fixed deal
+ends lets assume the rate increases by 0.4% each year plateauing at 7%:
+
+<pre>
+
+$ ./mcalc.pl -m=100000 -a=995 -t=20 -i=3.2 -it=3 -ii=0.4 -ic=7
+
+Mortgage value: 100000
+Arrangement fee added on: 995
+Term: 20 year(s)
+Interest rate: 3.2% (Monthly rate = 0.00266666666666667%)
+Interest rate term: 3 years
+Initial monthly payment: 570.28
+After initial term rate jumps by: 0.4
+---------------------------------------
+Total mortgage value: 100995
+---------------------------------------
+
+End of year 1    Mortgage: 97330.02   Total paid: 6843.37    Total interest: 3168.62     (Rate 3.2%, Monthly Payment 570.28)
+End of year 2    Mortgage: 93546.03   Total paid: 13686.75   Total interest: 6217.92     (Rate 3.2%, Monthly Payment 570.28)
+End of year 3    Mortgage: 89639.16   Total paid: 20530.12   Total interest: 9144.00     (Rate 3.2%, Monthly Payment 570.28)
+End of year 4    Mortgage: 85418.81   Total paid: 27908.29   Total interest: 12289.17    (Rate 3.6%, Monthly Payment 614.85)
+End of year 5    Mortgage: 81176.36   Total paid: 35490.29   Total interest: 15614.56    (Rate 4%, Monthly Payment 631.83)
+End of year 6    Mortgage: 76885.59   Total paid: 43266.97   Total interest: 19084.74    (Rate 4.4%, Monthly Payment 648.06)
+End of year 7    Mortgage: 72519.22   Total paid: 51228.62   Total interest: 22662.55    (Rate 4.8%, Monthly Payment 663.47)
+End of year 8    Mortgage: 68048.39   Total paid: 59364.89   Total interest: 26308.62    (Rate 5.2%, Monthly Payment 678.02)
+End of year 9    Mortgage: 63442.13   Total paid: 67664.83   Total interest: 29980.80    (Rate 5.6%, Monthly Payment 691.66)
+End of year 10   Mortgage: 58666.70   Total paid: 76116.88   Total interest: 33633.55    (Rate 6%, Monthly Payment 704.34)
+End of year 11   Mortgage: 53684.93   Total paid: 84708.87   Total interest: 37217.20    (Rate 6.4%, Monthly Payment 716.00)
+End of year 12   Mortgage: 48455.39   Total paid: 93427.99   Total interest: 40677.15    (Rate 6.8%, Monthly Payment 726.59)
+End of year 13   Mortgage: 42895.27   Total paid: 102203.85  Total interest: 43860.45    (Rate 7%, Monthly Payment 731.32)
+End of year 14   Mortgage: 36933.21   Total paid: 110979.71  Total interest: 46639.47    (Rate 7%, Monthly Payment 731.32)
+End of year 15   Mortgage: 30540.14   Total paid: 119755.57  Total interest: 48984.98    (Rate 7%, Monthly Payment 731.32)
+End of year 16   Mortgage: 23684.93   Total paid: 128531.43  Total interest: 50865.63    (Rate 7%, Monthly Payment 731.32)
+End of year 17   Mortgage: 16334.14   Total paid: 137307.29  Total interest: 52247.83    (Rate 7%, Monthly Payment 731.32)
+End of year 18   Mortgage: 8451.97    Total paid: 146083.15  Total interest: 53095.54    (Rate 7%, Monthly Payment 731.32)
+End of year 19   Mortgage: 0.00       Total paid: 154859.01  Total interest: 53370.13    (Rate 7%, Monthly Payment 731.32)
+
+</pre>
+
+Lets now assume we manage to make a £75 overpayment each month:
+
+<pre>
+
+$ ./mcalc.pl -m=100000 -a=995 -t=20 -i=3.2 -it=3 -ii=0.4 -ic=7 -o=75
+
+Mortgage value: 100000
+Arrangement fee added on: 995
+Term: 20 year(s)
+Interest rate: 3.2% (Monthly rate = 0.00266666666666667%)
+Interest rate term: 3 years
+Initial monthly payment: 570.28
+After initial term rate jumps by: 0.4%
+Cap rate jumps at: 7%
+---------------------------------------
+Total mortgage value: 100995
+---------------------------------------
+
+End of year 1    Mortgage: 96416.70   Total paid: 6843.37    Total interest: 3152.87     (Rate 3.2%, Monthly Payment 570.28 Overpayment 75.00)
+End of year 2    Mortgage: 91689.74   Total paid: 13686.75   Total interest: 6156.67     (Rate 3.2%, Monthly Payment 570.28 Overpayment 75.00)
+End of year 3    Mortgage: 86809.27   Total paid: 20530.12   Total interest: 9006.56     (Rate 3.2%, Monthly Payment 570.28 Overpayment 75.00)
+End of year 4    Mortgage: 81807.16   Total paid: 27675.37   Total interest: 12034.69    (Rate 3.6%, Monthly Payment 595.44 Overpayment 75.00)
+End of year 5    Mortgage: 76827.39   Total paid: 34936.78   Total interest: 15199.74    (Rate 4%, Monthly Payment 605.12 Overpayment 75.00)
+End of year 6    Mortgage: 71848.12   Total paid: 42296.84   Total interest: 18462.27    (Rate 4.4%, Monthly Payment 613.34 Overpayment 75.00)
+End of year 7    Mortgage: 66847.77   Total paid: 49736.84   Total interest: 21781.92    (Rate 4.8%, Monthly Payment 620.00 Overpayment 75.00)
+End of year 8    Mortgage: 61804.83   Total paid: 57236.81   Total interest: 25117.09    (Rate 5.2%, Monthly Payment 625.00 Overpayment 75.00)
+End of year 9    Mortgage: 56697.73   Total paid: 64775.21   Total interest: 28424.56    (Rate 5.6%, Monthly Payment 628.20 Overpayment 75.00)
+End of year 10   Mortgage: 51504.80   Total paid: 72328.74   Total interest: 31659.20    (Rate 6%, Monthly Payment 629.46 Overpayment 75.00)
+End of year 11   Mortgage: 46204.32   Total paid: 79871.84   Total interest: 34773.55    (Rate 6.4%, Monthly Payment 628.59 Overpayment 75.00)
+End of year 12   Mortgage: 40774.90   Total paid: 87376.02   Total interest: 37717.53    (Rate 6.8%, Monthly Payment 625.35 Overpayment 75.00)
+End of year 13   Mortgage: 35166.64   Total paid: 94760.84   Total interest: 40361.39    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 14   Mortgage: 29152.97   Total paid: 102145.67  Total interest: 42597.47    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 15   Mortgage: 22704.57   Total paid: 109530.50  Total interest: 44396.29    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 16   Mortgage: 15790.02   Total paid: 116915.33  Total interest: 45726.22    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 17   Mortgage: 8375.61    Total paid: 124300.16  Total interest: 46553.39    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 18   Mortgage: 425.21     Total paid: 131684.99  Total interest: 46841.45    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+End of year 19   Mortgage: -262.71    Total paid: 132300.39  Total interest: 46839.92    (Rate 7%, Monthly Payment 615.40 Overpayment 75.00)
+Paid off in month 1 of year 19
+
+</pre>
+
+Apparently that 75 quid overpayment brings down the compulsory payments in the,
+second half of the term by £100 and shaves a year off the mortage term.
+
+Revisiting this script again now a few years later I could still sit here plugging
+in different variables and seeing how it affects the payments in ways I'd never have
+thought of otherwise.  I also notice it's far from the greatest example of perl 
+scripting ever; if I ever get time I'll rewrite it.
diff --git a/mcalc.pl b/mcalc.pl
new file mode 100755
index 0000000..6bb7578
--- /dev/null
+++ b/mcalc.pl
@@ -0,0 +1,123 @@
+#!/usr/bin/perl
+
+# Glyn Astill <glyn@8kb.co.uk> 11/10/2011
+
+use strict;
+use Getopt::Long qw/GetOptions/;
+Getopt::Long::Configure('no_ignore_case');
+
+my $debug = 0;
+my $USAGE = '-m <mortgage value> -a <arrangement fee> -i <interest rate>';
+
+my $mortgage_value;
+my $arrangement_fee;
+my $interest_rate;
+my $interest_rate_term;
+my $monthly_payment;
+my $term;
+my $interest_rate_increase;
+my $cap_rate_increase;
+my $monthly_overpayment;
+
+my $year;
+my $month;
+
+my $total_mortgage;
+my $monthly_interest;
+my $month_value;
+my $total_paid;
+my $interest_accrued;
+
+##http://www.perl.com/doc/manual/html/lib/Getopt/Long.html
+use vars qw{%opt};
+die $USAGE unless 
+	GetOptions(\%opt,
+		   'mortgage_value|m=n',
+		   'arrangement_fee|a=n',
+		   'interest_rate|i=f',
+		   'interest_rate_term|it=n',
+		   'term|t=n',
+		   'interest_rate_increase|ii=f',
+		   'cap_rate_increase|ic=f',
+		   'monthly_overpayment|o=n',
+		   'monthly_payment|p=n',
+		   )
+	and keys %opt
+	and ! @ARGV;
+	
+## initial call ... $ARGV[0] and $ARGV[1] are the command line arguments
+
+$mortgage_value = $opt{mortgage_value};
+$arrangement_fee = ($opt{arrangement_fee} // 0);
+$interest_rate = ($opt{interest_rate} // 5);
+$interest_rate_term = ($opt{interest_rate_term} // 1);
+$monthly_payment = ($opt{monthly_payment} // 0);
+$term = ($opt{term} // 25);
+$interest_rate_increase = ($opt{interest_rate_increase} // 0);
+$cap_rate_increase = $opt{cap_rate_increase};
+$monthly_overpayment = ($opt{monthly_overpayment} // 0);
+
+$total_mortgage = $mortgage_value+$arrangement_fee;
+$monthly_interest = ($interest_rate/100)/12;
+
+$month_value = $total_mortgage;
+if (! $monthly_payment) {
+	$monthly_payment = (($month_value*$monthly_interest)/(1-((1+$monthly_interest)**($term*12*-1))));
+}
+
+print "\nMortgage value: ",$mortgage_value,"\n";
+print "Arrangement fee added on: ",$arrangement_fee, "\n";
+print "Term: ", $term, " year(s)\n";
+print "Interest rate: ",$interest_rate, "% (Monthly rate = ", $monthly_interest, "%)\n";
+print "Interest rate term: ",$interest_rate_term, " years\n";
+print "Initial monthly payment: ", sprintf("%.2f", $monthly_payment) ,"\n";
+print "After initial term rate jumps by: ",$interest_rate_increase,"%\n";
+print "Cap rate jumps at: ",$cap_rate_increase,"%\n" if ($cap_rate_increase);
+print "---------------------------------------\n";
+print "Total mortgage value: ",$total_mortgage,"\n";
+print "---------------------------------------\n\n";
+
+do_it: {
+	for ($year = 1; $year < $term; $year++) {
+		if ($year > $interest_rate_term) {
+			if ((! $cap_rate_increase) || ($interest_rate < $cap_rate_increase)) {
+				$interest_rate = $interest_rate + $interest_rate_increase;
+			 	if ($interest_rate < 0) {
+					$interest_rate=0.0000000001;
+				}
+				elsif ($cap_rate_increase && ($interest_rate > $cap_rate_increase)) {
+					$interest_rate = $cap_rate_increase;
+				}	
+				$monthly_interest = ($interest_rate/100)/12;
+				$monthly_payment = (($month_value*$monthly_interest)/(1-((1+$monthly_interest)**(($term-$year)*12*-1))));
+			}
+		}
+
+		for ($month = 1; $month <= 12; $month++) {		
+			$month_value = $month_value+($month_value*$monthly_interest)-($monthly_payment+$monthly_overpayment);
+			$total_paid = $total_paid + $monthly_payment;
+			$interest_accrued = $interest_accrued + ($month_value*$monthly_interest);
+			if (($month == 12) || ($month_value <= 0)){
+				print "End of year ", pack("A5",$year);
+				print "Mortgage: ", pack("A11",sprintf("%.2f", $month_value));
+				print "Total paid: ", pack("A11", sprintf("%.2f", $total_paid));
+				print "Total interest: ", pack("A11", sprintf("%.2f", $interest_accrued));
+				print " (Rate ", $interest_rate, "%, Monthly Payment ", sprintf("%.2f", $monthly_payment);
+
+				if ($monthly_overpayment > 0) {
+					print " Overpayment ", sprintf("%.2f", $monthly_overpayment);
+				}
+
+				print ")\n";
+				
+				if ($month_value <= 0) {
+					print "Paid off in month ", $month, " of year ", $year, "\n";
+					last do_it;
+				}
+
+			}
+		}
+	 }
+ }
+ 
+__END__