= mortgage_calc

http://www.pathf.com/blogs/2010/02/mortcalc-gem/

Calculates mortgage APR, monthly payments, and fees.

== INSTALL $ sudo gem install gemcutter $ gem tumble $ sudo gem install mortgage_calc or add the following to your environment.rb config.gem 'mortgage_calc'

==Example: loan_amount = 350000 interest_rate = 4.75 period = 30 * 12 lender_fee = 800 points = 1.0

mort_calc = MortgageCalc::MortgageUtil.new(loan_amount, interest_rate, period, lender_fee, points)

mort_calc.apr
mort_calc.monthly_payment
mort_calc.monthly_payment_with_fees
mort_calc.total_fees

==Formulas used ===Monthly payment with fees P = [(C + E) r (1 + r)^N]/[(1 + r)^N - 1]

P = monthly payment
C = Loan amount
r = Interest rate
N = Period in months
E = Lender fees

===Monthly payment without fees is calculated like above with E = 0.

===APR [a (1 + a)^N] / [(1 + a)^N - 1] - P/C = 0 a = A/1200 N = Period in months P = Monthly payment C = Loan amount

===Total fees Total fees are calculated simply by adding Lender fees to the points paid by borrower. T = E + P(C)