Mortgage Payment Calculator
body {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
line-height: 1.6;
color: #333;
max-width: 800px;
margin: 0 auto;
padding: 20px;
}
.calc-container {
background: #f8f9fa;
border: 1px solid #e9ecef;
border-radius: 8px;
padding: 30px;
margin-bottom: 40px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-title {
text-align: center;
margin-bottom: 25px;
color: #2c3e50;
}
.form-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
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@media (max-width: 600px) {
.form-grid {
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.input-group label {
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.input-group input {
width: 100%;
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border-radius: 4px;
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.input-group input:focus {
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.btn-calc {
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color: white;
border: none;
padding: 15px;
font-size: 18px;
font-weight: bold;
border-radius: 4px;
cursor: pointer;
transition: background-color 0.2s;
margin-top: 10px;
width: 100%;
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.btn-calc:hover {
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#results-area {
display: none;
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border-radius: 6px;
padding: 20px;
margin-top: 25px;
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.error-msg {
color: #dc3545;
text-align: center;
margin-top: 10px;
display: none;
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background: #fff;
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h2 {
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border-bottom: 2px solid #007bff;
padding-bottom: 10px;
margin-top: 40px;
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h3 {
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ul {
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li {
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Mortgage Payment Calculator
Please enter valid positive numbers for all fields.
Principal & Interest:
$0.00
Property Tax (Monthly):
$0.00
Home Insurance (Monthly):
$0.00
Total Monthly Payment:
$0.00
Understanding Your Mortgage Calculation
Buying a home is one of the largest financial decisions you will make. This Mortgage Payment Calculator helps you estimate your monthly financial commitment by breaking down the costs associated with homeownership. Understanding how these numbers are derived is crucial for budgeting effectively.
How the Mortgage Formula Works
A standard mortgage payment is calculated using the amortization formula. This determines the fixed monthly payment required to pay off the loan principal and interest over a specific term.
The core formula used is:
M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1 ]
- M = Total monthly payment
- P = Principal loan amount (Home Price minus Down Payment)
- i = Monthly interest rate (Annual Rate divided by 12)
- n = Number of payments (Loan Term in years multiplied by 12)
Components of Your Monthly Payment (PITI)
Lenders often refer to your payment as "PITI," which stands for Principal, Interest, Taxes, and Insurance.
1. Principal
This is the portion of your payment that goes toward reducing the outstanding balance of your loan. In the early years of a mortgage, the principal portion is small, but it increases over time as the interest portion decreases.
2. Interest
This is the cost of borrowing money from the lender. Your interest rate is determined by economic factors and your personal creditworthiness. A lower interest rate can save you tens of thousands of dollars over the life of the loan.
3. Property Taxes
Local governments assess property taxes to fund public services like schools and roads. This calculator estimates the monthly portion of your annual tax bill. Lenders typically collect this monthly and hold it in an escrow account to pay the tax bill when it is due.
4. Homeowners Insurance
Insurance protects your property against damage from fire, theft, and other hazards. Like property taxes, this is usually paid annually but collected in monthly installments by your lender via an escrow account.
Tips for Lowering Your Monthly Payment
- Increase your Down Payment: Putting more money down reduces the principal loan amount (P), directly lowering your monthly P&I payment.
- Improve Your Credit Score: A higher credit score often qualifies you for a lower interest rate.
- Shop for Insurance: Homeowners insurance premiums vary by provider. Comparing quotes can help you find a more affordable policy.
- Eliminate PMI: If your down payment is less than 20%, you may have to pay Private Mortgage Insurance (PMI). Saving for a 20% down payment removes this extra cost.
function calculateMortgage() {
// 1. Get Input Values
var homePrice = document.getElementById("homePrice").value;
var downPayment = document.getElementById("downPayment").value;
var interestRate = document.getElementById("interestRate").value;
var loanTerm = document.getElementById("loanTerm").value;
var propertyTax = document.getElementById("propertyTax").value;
var homeInsurance = document.getElementById("homeInsurance").value;
var resultArea = document.getElementById("results-area");
var errorMsg = document.getElementById("error-message");
// 2. Validate Inputs
// Check if values are empty or not numbers
if (homePrice === "" || downPayment === "" || interestRate === "" || loanTerm === "") {
errorMsg.style.display = "block";
resultArea.style.display = "none";
return;
}
// Parse values to floats
var pPrice = parseFloat(homePrice);
var pDown = parseFloat(downPayment);
var pRate = parseFloat(interestRate);
var pTerm = parseFloat(loanTerm);
var pTax = parseFloat(propertyTax) || 0; // Default to 0 if empty
var pIns = parseFloat(homeInsurance) || 0; // Default to 0 if empty
// Logic check for negative numbers
if (pPrice < 0 || pDown < 0 || pRate < 0 || pTerm = home price
if (principal <= 0) {
var totalMonthly = (pTax / 12) + (pIns / 12);
displayResults(0, pTax/12, pIns/12, totalMonthly);
return;
}
// Monthly Interest Rate (r)
var monthlyRate = (pRate / 100) / 12;
// Total Number of Payments (n)
var numberOfPayments = pTerm * 12;
// Amortization Formula: M = P * [r(1+r)^n] / [(1+r)^n – 1]
var monthlyPI = 0;
if (pRate === 0) {
// Handle 0% interest edge case
monthlyPI = principal / numberOfPayments;
} else {
var numerator = monthlyRate * Math.pow((1 + monthlyRate), numberOfPayments);
var denominator = Math.pow((1 + monthlyRate), numberOfPayments) – 1;
monthlyPI = principal * (numerator / denominator);
}
var monthlyTax = pTax / 12;
var monthlyIns = pIns / 12;
var totalMonthlyPayment = monthlyPI + monthlyTax + monthlyIns;
// 4. Display Results
displayResults(monthlyPI, monthlyTax, monthlyIns, totalMonthlyPayment);
}
function displayResults(pi, tax, ins, total) {
var errorMsg = document.getElementById("error-message");
var resultArea = document.getElementById("results-area");
// Hide error, show results
errorMsg.style.display = "none";
resultArea.style.display = "block";
// Format Currency
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
minimumFractionDigits: 2
});
document.getElementById("result-pi").innerHTML = formatter.format(pi);
document.getElementById("result-tax").innerHTML = formatter.format(tax);
document.getElementById("result-ins").innerHTML = formatter.format(ins);
document.getElementById("result-total").innerHTML = formatter.format(total);
}