Understanding your monthly financial commitment is the first step in the home buying journey. This Mortgage Payment Calculator is designed to help you estimate your total monthly payment, including principal, interest, taxes, and insurance (PITI). By adjusting the home price, down payment, and interest rate, you can determine a budget that fits your financial goals.
30 Years
20 Years
15 Years
10 Years
Please enter valid positive numbers for all fields.
Estimated Monthly Payment$0.00
Principal & Interest:$0.00
Property Tax (Monthly):$0.00
Home Insurance (Monthly):$0.00
Total Loan Amount:$0.00
How Your Mortgage is Calculated
The standard formula for calculating mortgage payments is based on the amortization of the principal loan amount over the term of the loan. While the math can be complex, understanding the components is straightforward:
Principal: The amount of money you borrow from the lender. This is usually the home price minus your down payment.
Interest: The cost of borrowing money, expressed as a percentage rate. In the early years of a mortgage, a larger portion of your payment goes toward interest.
Taxes & Insurance (Escrow): Most lenders require you to pay 1/12th of your annual property taxes and homeowners insurance each month. These funds are held in an escrow account and paid on your behalf when due.
Factors That Impact Your Monthly Payment
Several variables can significantly change how much you pay every month:
1. Down Payment Size
A larger down payment reduces your principal loan amount. Additionally, if you put down less than 20%, you may be required to pay Private Mortgage Insurance (PMI), which increases your monthly costs.
2. Loan Term
Choosing a 15-year term instead of a 30-year term will increase your monthly payment because you are paying off the principal faster. However, you will pay significantly less in total interest over the life of the loan.
3. Interest Rate
Even a fractional difference in interest rates (e.g., 6.5% vs 7.0%) can result in thousands of dollars of difference over the lifespan of a 30-year mortgage. Your credit score typically determines the rate you qualify for.
Frequently Asked Questions
Does this calculator include HOA fees?
This specific calculator focuses on PITI (Principal, Interest, Taxes, and Insurance). If you are buying a condo or a home in a managed community, you should add your monthly HOA dues on top of the estimated total provided above.
What is a good debt-to-income ratio?
Lenders look at your Debt-to-Income (DTI) ratio to determine how much you can borrow. Generally, lenders prefer a DTI below 36%, meaning your total monthly debt payments (including your new mortgage) should not exceed 36% of your gross monthly income.
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 = parseInt(document.getElementById('loanTerm').value);
var annualTax = parseFloat(document.getElementById('propertyTax').value);
var annualInsurance = parseFloat(document.getElementById('homeInsurance').value);
// 2. Validate Inputs
var errorDiv = document.getElementById('mcErrorMessage');
var resultDiv = document.getElementById('mcResult');
// Check if values are valid numbers. Allow 0 for downpayment/tax/insurance
if (isNaN(homePrice) || homePrice <= 0 ||
isNaN(interestRate) || interestRate < 0 ||
isNaN(loanTermYears) ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(annualTax) || annualTax < 0 ||
isNaN(annualInsurance) || annualInsurance < 0) {
errorDiv.style.display = 'block';
resultDiv.style.display = 'none';
return;
}
// Hide error if validation passes
errorDiv.style.display = 'none';
// 3. Perform Calculations
// Principal Loan Amount
var principal = homePrice – downPayment;
if (principal <= 0) {
errorDiv.innerHTML = "Down payment cannot be greater than Home Price.";
errorDiv.style.display = 'block';
resultDiv.style.display = 'none';
return;
}
// Monthly Interest Rate
var monthlyRate = (interestRate / 100) / 12;
// Total Number of Payments
var numberOfPayments = loanTermYears * 12;
// Calculate Monthly P&I (Principal & Interest)
// 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 + monthlyRate, numberOfPayments);
monthlyPrincipalInterest = principal * ((monthlyRate * mathPower) / (mathPower – 1));
}
// Calculate Monthly Tax and Insurance
var monthlyTax = annualTax / 12;
var monthlyInsurance = annualInsurance / 12;
// Total Monthly Payment
var totalMonthlyPayment = monthlyPrincipalInterest + monthlyTax + monthlyInsurance;
// 4. Update the UI
document.getElementById('displayPrincipalInterest').innerText = '$' + monthlyPrincipalInterest.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayTax').innerText = '$' + monthlyTax.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayInsurance').innerText = '$' + monthlyInsurance.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayTotalMonthly').innerText = '$' + totalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('displayLoanAmount').innerText = '$' + principal.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
// Show Result Div
resultDiv.style.display = 'block';
}