www.pathf.com/blogs/2010/02/mortcalc-gem/
Calculates mortgage APR, monthly payments, and fees.
$ sudo gem install gemcutter $ gem tumble $ sudo gem install mortgage_calc
or add the following to your environment.rb
config.gem 'mortgage_calc'
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
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
[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 are calculated simply by adding Lender fees to the points paid by borrower.
T = E + P(C)