mortgage_calculations¶ ↑
www.pathf.com/blogs/2010/02/mortcalc-gem/
Calculates mortgage APR and monthly payments.
INSTALL¶ ↑
$ sudo gem install mortgage_calculations
or add following to your Gemfile
gem "mortgage_calculations", :require => "mortgage_calc"
or add the following to your environment.rb
config.gem 'mortgage_calculations', :lib => "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, total_fees, period) mort_calc.apr mort_calc.monthly_payment mort_calc.monthly_payment_with_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)