/mortgage-calculator

Library for calculating the maximum mortgage and amortization tables.

Primary LanguageJavaScript

Mortgage Calculator

Codeship Status for cristobal-io/mortgage-calculator Build Status Coverage Status

Demo website

This is a node module that allows you to calculate the maximum mortgage that you can afford based on your salary and the initial Deposit you will make.

It is based on the assumption that no more than 36% of your salary before taxes should be designated to the mortgage to avoid financial problems.

You can check the article about the Underwriter for more information.

The maximum allowed by law is a 43% before taxes, however many articles suggest that you shouldn't take a mortgage over 36%.

Formulas

  • The formula used to obtain the payment:

payment

  • The formula used to obtain the mortgage 1 :

mortgage_formula

Installation.

npm install mortgage-calculator

or download the minified version

Usage.

on node.js

var mortgageCalculator = require("mortgage-calculator");

On the browser.

window.mortgageCalculator will be exposed after including the script.

<script src="morgage-calculator.min.js"></script>

Methods.

mortgageCalculator.getMaxMortgage

This method will tell you the price of the house that you can afford. The value returned will be an object with numbers.

mortgageCalculator.calculateMortgage(options);
options
  • initialDeposit: How much money will you pay upfront.
  • monthlyIncome: Gross monthly income.
  • interest: Interest rate.
  • term: Duration in years of the mortgage. Default: 10
  • payments: number of payments, the term has priority, if no term is provided, will use payments, if no payments are provided, it will use the term's default.
  • monthlyExpenses: Personal monthly expenses.
  • age: Age of the youngest person taking the loan.
  • settings: (optional)
    • maxAge: Maximum age restricts the length of the term. Default: 65
    • riskRate: Maximum percent of risk. Default:36
    • (personalTaxRate: Percent of the monthly income that is paid as taxes. Default: 42.) -> future version.
Example:
// when calling the function
mortgageCalculator.calculateMortgage({
      "initialDeposit": 20000,
      "monthlyIncome": 2000,
      "interest": 3,
      "term": 20,
      "monthlyExpenses": 800
    })
// Will return an object like this one.
Object {
  maxMonthlyPayment: 432,
  totalPriceHouse: 97894.3150262,
  mortgageTotal: 77894.3150262,
  totalInterest: 1509.0217746
}

mortgageCalculator.formatMoney

This method will format an integer to the desired localized format. The value returned will be an string.

mortgageCalculator.formatMoney(number, options);
number

This will be the value you want to format.

options
  • symbol: Default "$"
  • places: Default 2
  • thousand: Default ","
  • decimal: Default "."
Example
// Calling the function with this argument
mortgageCalculator.formatMoney(123456789.1234567);

// returns the default format 
"$123,456,789.12"

mortgageCalculator.amortization

This method will give you the table of amortization.

mortgageCalculator.amortization(capital, pay, periods, interest);
capital

Total value of the mortgage we want to obtain the amortization table for.

pay

Calculated monthly pay obtained from mortgageCalculator.getMaxMortgage

periods

Number of payments for the amortization.

interest

Annual interest not expressed in %

example:
3% --> 3/100 = 0.03
Example
// When calling the function with the following parameters
mortgageCalculator.amortization(5000, 423.47, 12, 0.03);

// will return the following (abbreviated)
  {
  "period": 1,
  "amortizationInterest": 12.5,
  "amortizationCapital": 410.97,
  "remainingCapital": 4589.03
}, {
  "period": 2,
  "amortizationInterest": 11.472574999999999,
  "amortizationCapital": 411.997425,
  "remainingCapital": 4177.032574999999
}, {
  "period": 3,
  "amortizationInterest": 10.442581437499998,
  "amortizationCapital": 413.02741856250003,
  "remainingCapital": 3764.0051564374994
}, {
  "period": 4,
  "amortizationInterest": 9.410012891093748,
  "amortizationCapital": 414.0599871089063,
  "remainingCapital": 3349.9451693285932
},
.
.
// abbreviated
.
.
{
  "period": 12,
  "amortizationInterest": 1.0559892142203449,
  "amortizationCapital": 422.395685688138,
  "remainingCapital": 0
}

Contributor notes:

To start run:

make setup

For test use command:

make test

For test on Browsers use testem:

make testem

Notes:

1: This formula comes from:

payment