Advanced Mortgage Calculator
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Estimated Monthly Payment
$0.00
Principal & Interest:
$0.00
Property Tax:
$0.00
Home Insurance:
$0.00
HOA Fees:
$0.00
Loan Amount:
$0.00
Total Interest Cost:
$0.00
How a Mortgage Calculator Helps You
Purchasing a home is likely the largest financial commitment you will make in your lifetime. Understanding the monthly breakdown of costs is crucial for financial stability. This mortgage calculator provides a comprehensive view of what you can expect to pay each month, going beyond just the loan repayment.
Understanding the Components
Your monthly housing payment typically consists of four main parts, often referred to as PITI:
- Principal: The money that goes towards paying down your loan balance.
- Interest: The cost of borrowing money, paid to the lender.
- Taxes: Property taxes charged by your local government, usually collected by the lender in an escrow account.
- Insurance: Homeowners insurance to protect against damage, also often collected via escrow.
Additionally, if you buy a condo or a home in a planned community, you may have HOA (Homeowners Association) fees, which are included in this calculator's estimation.
Tips for Lowering Your Payment
If the estimated payment is higher than your budget allows, consider these strategies:
- Increase Down Payment: A larger down payment reduces the principal loan amount and can lower your interest rate.
- Improve Credit Score: A higher credit score often qualifies you for lower interest rates.
- Choose a Longer Term: While a 30-year term has more total interest than a 15-year term, the monthly payments are significantly lower.
- Shop for Insurance: Homeowners insurance rates vary; shopping around can save you hundreds per year.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById('homePrice').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var loanTermYears = parseFloat(document.getElementById('loanTerm').value);
var propertyTaxAnnual = parseFloat(document.getElementById('propertyTax').value);
var homeInsuranceAnnual = parseFloat(document.getElementById('homeInsurance').value);
var hoaFeesMonthly = parseFloat(document.getElementById('hoaFees').value);
// 2. Validate Inputs (Simple check to prevent NaN errors)
if (isNaN(homePrice) || homePrice < 0) homePrice = 0;
if (isNaN(downPayment) || downPayment < 0) downPayment = 0;
if (isNaN(interestRate) || interestRate < 0) interestRate = 0;
if (isNaN(propertyTaxAnnual) || propertyTaxAnnual < 0) propertyTaxAnnual = 0;
if (isNaN(homeInsuranceAnnual) || homeInsuranceAnnual < 0) homeInsuranceAnnual = 0;
if (isNaN(hoaFeesMonthly) || hoaFeesMonthly < 0) hoaFeesMonthly = 0;
// 3. Calculate Loan Variables
var principal = homePrice – downPayment;
// Handle case where down payment exceeds home price
if (principal < 0) principal = 0;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// 4. Calculate Monthly Principal & Interest (Amortization Formula)
// Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
var monthlyPrincipalAndInterest = 0;
if (interestRate === 0) {
monthlyPrincipalAndInterest = principal / numberOfPayments;
} else {
var x = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalAndInterest = principal * ((monthlyInterestRate * x) / (x – 1));
}
// Handle edge case if principal is 0
if (principal <= 0) monthlyPrincipalAndInterest = 0;
// 5. Calculate Other Monthly Costs
var monthlyPropertyTax = propertyTaxAnnual / 12;
var monthlyHomeInsurance = homeInsuranceAnnual / 12;
var totalMonthlyPayment = monthlyPrincipalAndInterest + monthlyPropertyTax + monthlyHomeInsurance + hoaFeesMonthly;
// 6. Calculate Totals for Report
var totalCostOfLoan = (monthlyPrincipalAndInterest * numberOfPayments);
var totalInterestPaid = totalCostOfLoan – principal;
// 7. Update UI with formatted numbers
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById('totalMonthlyPayment').innerHTML = formatter.format(totalMonthlyPayment);
document.getElementById('resPrincipalInterest').innerHTML = formatter.format(monthlyPrincipalAndInterest);
document.getElementById('resPropertyTax').innerHTML = formatter.format(monthlyPropertyTax);
document.getElementById('resHomeInsurance').innerHTML = formatter.format(monthlyHomeInsurance);
document.getElementById('resHoaFees').innerHTML = formatter.format(hoaFeesMonthly);
document.getElementById('resLoanAmount').innerHTML = formatter.format(principal);
document.getElementById('resTotalInterest').innerHTML = formatter.format(totalInterestPaid);
// Show results area
document.getElementById('resultsArea').style.display = 'block';
}