Please enter valid positive numbers for all fields.
Monthly Payment Breakdown
Principal & Interest:$0.00
Property Tax:$0.00
Homeowner's Insurance:$0.00
HOA Fees:$0.00
Total Monthly Payment:$0.00
Loan Amount: $0.00
How to Calculate Your Monthly Mortgage Payment
Understanding your estimated monthly housing costs is the first critical step in the home buying process. This Mortgage Payment Calculator helps you estimate not just the repayment of your loan (Principal and Interest), but also the "hidden" costs that are often escrowed, such as property taxes and insurance.
The Components of a Mortgage Payment (PITI)
Mortgage lenders often use the acronym PITI to describe the total monthly cost of a mortgage. Here is what each letter represents and how it affects your wallet:
Principal: The portion of your payment that goes directly toward reducing the loan balance.
Interest: The cost of borrowing money. In the early years of a mortgage, a higher percentage of your payment goes toward interest.
Taxes: Property taxes assessed by your local government. These are usually divided by 12 and paid monthly into an escrow account.
Insurance: Homeowners insurance protects the property against damage. Like taxes, this is often paid monthly via escrow.
How Interest Rates Affect Your Buying Power
Even a small difference in interest rates can have a significant impact on your monthly payment and the total cost of the loan over 30 years. For example, on a $300,000 loan, a 1% increase in interest rate can raise your monthly payment by hundreds of dollars, significantly reducing the price of the home you can afford.
Why Include HOA Fees?
If you are buying a condo or a home in a planned community, Homeowners Association (HOA) fees are mandatory. While these are rarely paid to the mortgage lender directly, they are a recurring monthly debt obligation that lenders consider when calculating your Debt-to-Income (DTI) ratio. Always include them in your calculation to get a true picture of affordability.
function calculateMortgage() {
// 1. Get input values by ID
var priceInput = document.getElementById('mp-price');
var downInput = document.getElementById('mp-down');
var rateInput = document.getElementById('mp-rate');
var termInput = document.getElementById('mp-term');
var taxInput = document.getElementById('mp-tax');
var insInput = document.getElementById('mp-insurance');
var hoaInput = document.getElementById('mp-hoa');
var resultDiv = document.getElementById('mp-result');
var errorDiv = document.getElementById('mp-error');
// 2. Parse values
var price = parseFloat(priceInput.value);
var down = parseFloat(downInput.value);
var annualRate = parseFloat(rateInput.value);
var years = parseFloat(termInput.value);
var annualTax = parseFloat(taxInput.value);
var annualIns = parseFloat(insInput.value);
var monthlyHoa = parseFloat(hoaInput.value);
// 3. Validation
if (isNaN(price) || isNaN(down) || isNaN(annualRate) || isNaN(years) ||
isNaN(annualTax) || isNaN(annualIns) || isNaN(monthlyHoa) ||
price < 0 || years <= 0) {
errorDiv.style.display = 'block';
resultDiv.style.display = 'none';
return;
}
// Clear error
errorDiv.style.display = 'none';
// 4. Calculation Logic
var loanAmount = price – down;
if (loanAmount price
loanAmount = 0;
}
var monthlyRate = (annualRate / 100) / 12;
var numberOfPayments = years * 12;
var monthlyPI = 0;
// Standard Amortization Formula: M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
if (loanAmount > 0 && monthlyRate > 0) {
monthlyPI = loanAmount * (monthlyRate * Math.pow(1 + monthlyRate, numberOfPayments)) / (Math.pow(1 + monthlyRate, numberOfPayments) – 1);
} else if (loanAmount > 0 && monthlyRate === 0) {
// 0% interest case
monthlyPI = loanAmount / numberOfPayments;
}
var monthlyTax = annualTax / 12;
var monthlyIns = annualIns / 12;
var totalMonthly = monthlyPI + monthlyTax + monthlyIns + monthlyHoa;
// 5. Update HTML Output
document.getElementById('res-pi').innerHTML = '$' + monthlyPI.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-tax').innerHTML = '$' + monthlyTax.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-ins').innerHTML = '$' + monthlyIns.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-hoa').innerHTML = '$' + monthlyHoa.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-total').innerHTML = '$' + totalMonthly.toLocaleString('en-US', {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('res-loan-amount').innerHTML = '$' + loanAmount.toLocaleString('en-US', {minimumFractionDigits: 0, maximumFractionDigits: 0});
// Show result
resultDiv.style.display = 'block';
}