Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site aplvax.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!umcp-cs!aplvax!pmg From: pmg@aplvax.UUCP (P. Michael Guba) Newsgroups: net.invest Subject: Re: amortization schedule? Message-ID: <178@aplvax.UUCP> Date: Mon, 11-Nov-85 10:17:16 EST Article-I.D.: aplvax.178 Posted: Mon Nov 11 10:17:16 1985 Date-Received: Wed, 13-Nov-85 04:28:46 EST References: <10800001@uicsl> Reply-To: pmg@aplvax.UUCP (P. Michael Guba) Followup-To: net.invest Distribution: net Organization: JHU/Applied Physics Laboratory Lines: 53 In response to article <10800001@uicsl>: | Principle P, Interest (annual) I, Months (terms) N | | Q1?) What is the formula for calculating the amortization schedule? | I.e., given P,I,N, how do I calculate the monthly loan payment $D. The term Principal (P) is misleading to me so I have defined the following: PV = Present value of mortgage PMT = Monthly loan payment PMT = (PV * i/12)/[1 - (1 + i/12)**(-N)] where i = I/100 and ** is the exponential operator. | Q2?) For payment, M (1<=M<=N), how do I calculate the amount of interest | (and/or principle) that makes up the loan payment of that month. PV = Present value of mortgage at month M in mortgage PMT = Monthly loan payment PV = (PMT * 12/i) * [1 - (1 + i)**(-(N - M + 1))] Interest portion of payment = PV * i/12 Principal portion of payment = PMT - (PV * i/12) | Q3?) If my loan payments are $D dollars per month and I pay $(D+X) on the | loan, can I calculate how much earlier the loan will be paid back? PV = Present value of mortgage at month after making extra payment X N = number of payments necessary to pay back loan N = ln[PMT/(PMT - (PV * i/12))]/ln[1 + i/12] where ln[] in the natural log function | Q4?) Is this the correct spelling of 'principle'? The correct spelling is principal. If you have any other questions send me mail. Hope this helps, Mike -- P. Michael Guba ...seismo!umcp-cs!aplvax!pmg JHU/Applied Physics Lab Johns Hopkins Road Laurel, Maryland 20707 (301) 953-6829