Estimate your monthly payments, including taxes, insurance, and HOA fees.
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$
%
Years
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$
$
Please enter valid numeric values for all fields.
Total Monthly Payment
$0.00
Principal & Interest:$0.00
Property Tax (Mo):$0.00
Home Insurance (Mo):$0.00
HOA Fees:$0.00
Loan Amount:$0.00
Total Interest Cost:$0.00
Total Cost of Loan:$0.00
Payoff Date:–
How to Calculate Your Mortgage Payment
Understanding your monthly mortgage payment is the first step toward successful homeownership. While a "sticker price" on a home might look affordable, the actual monthly cash flow required involves several components beyond just repaying the loan balance.
The Components of a Mortgage Payment (PITI)
Lenders often refer to your monthly payment as PITI, which stands for Principal, Interest, Taxes, and Insurance.
Principal: The portion of your payment that goes toward reducing the loan balance. In the early years of a 30-year mortgage, this amount is small but grows over time.
Interest: The cost of borrowing money. Initially, the majority of your payment goes to interest.
Taxes: Property taxes assessed by your local government, usually held in escrow by the lender and paid annually or semi-annually.
Insurance: Homeowners insurance protects the property against damage. If you put down less than 20%, you may also pay Private Mortgage Insurance (PMI).
Pro Tip: Don't forget Homeowners Association (HOA) fees! These are paid separately from your mortgage but affect your monthly affordability and debt-to-income ratio.
How Interest Rates Affect Affordability
Even a small change in interest rates can significantly impact your purchasing power. For example, on a $400,000 loan, the difference between a 6% and a 7% interest rate is roughly $260 per month. Over the life of a 30-year loan, that 1% difference costs nearly $93,000 in additional interest.
Determining Your Budget
Most financial experts recommend following the 28/36 rule. This rule suggests that your housing expenses (PITI) should not exceed 28% of your gross monthly income, and your total debt payments (including car loans, student loans, and credit cards) should not exceed 36%.
Amortization Explained
Amortization is the process of spreading out a loan into a series of fixed payments over time. While your total monthly payment remains the same (assuming a fixed-rate mortgage), the allocation changes. Your first payment might be 80% interest and 20% principal, while your final payment might be 1% interest and 99% principal.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = parseFloat(document.getElementById('mc_home_price').value);
var downPayment = parseFloat(document.getElementById('mc_down_payment').value);
var interestRate = parseFloat(document.getElementById('mc_interest_rate').value);
var loanTermYears = parseFloat(document.getElementById('mc_loan_term').value);
var propertyTaxYearly = parseFloat(document.getElementById('mc_property_tax').value);
var homeInsuranceYearly = parseFloat(document.getElementById('mc_home_insurance').value);
var hoaFeesMonthly = parseFloat(document.getElementById('mc_hoa_fees').value);
var errorDiv = document.getElementById('mc_error');
var resultsDiv = document.getElementById('mc_results');
// 2. Validation
if (isNaN(homePrice) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTermYears) ||
isNaN(propertyTaxYearly) || isNaN(homeInsuranceYearly)) {
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
}
// Handle HOA default if empty
if (isNaN(hoaFeesMonthly)) {
hoaFeesMonthly = 0;
}
errorDiv.style.display = 'none';
// 3. Calculation Logic
var principal = homePrice – downPayment;
// Handle edge case where down payment > home price
if (principal < 0) principal = 0;
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfPayments = loanTermYears * 12;
// Mortgage Payment Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
var monthlyPrincipalInterest = 0;
if (interestRate === 0) {
monthlyPrincipalInterest = principal / numberOfPayments;
} else {
var mathPower = Math.pow(1 + monthlyInterestRate, numberOfPayments);
monthlyPrincipalInterest = principal * ((monthlyInterestRate * mathPower) / (mathPower – 1));
}
var monthlyTax = propertyTaxYearly / 12;
var monthlyInsurance = homeInsuranceYearly / 12;
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance + hoaFeesMonthly;
var totalInterestPaid = (monthlyPrincipalInterest * numberOfPayments) – principal;
var totalCostOfLoan = (totalMonthlyPayment * numberOfPayments);
// Note: Total cost usually refers to Principal + Interest, but user cares about total cash outflow usually.
// Let's standardise Total Cost as Principal + Total Interest (Loan Cost only)
var totalLoanCost = principal + totalInterestPaid;
// Calculate Payoff Date
var today = new Date();
var payoffDate = new Date(today.setMonth(today.getMonth() + numberOfPayments));
var options = { month: 'long', year: 'numeric' };
var payoffDateString = payoffDate.toLocaleDateString('en-US', options);
// 4. Formatting Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
// 5. Update UI
document.getElementById('mc_total_monthly').innerText = formatter.format(totalMonthlyPayment);
document.getElementById('mc_pi_monthly').innerText = formatter.format(monthlyPrincipalInterest);
document.getElementById('mc_tax_monthly').innerText = formatter.format(monthlyTax);
document.getElementById('mc_ins_monthly').innerText = formatter.format(monthlyInsurance);
document.getElementById('mc_hoa_display').innerText = formatter.format(hoaFeesMonthly);
document.getElementById('mc_loan_amount').innerText = formatter.format(principal);
document.getElementById('mc_total_interest').innerText = formatter.format(totalInterestPaid);
document.getElementById('mc_total_cost').innerText = formatter.format(totalLoanCost);
document.getElementById('mc_payoff_date').innerText = payoffDateString;
resultsDiv.style.display = 'block';
}