This calculator helps you estimate how much house you can afford based on your income, debts, and desired mortgage terms. It considers your gross monthly income, existing monthly debt payments, the estimated interest rate, and the loan term.
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 500px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
margin-bottom: 15px;
color: #333;
}
.form-group {
margin-bottom: 15px;
}
.form-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.form-group input[type="number"] {
width: calc(100% – 12px);
padding: 8px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calculator-container button {
display: block;
width: 100%;
padding: 10px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
margin-top: 20px;
}
.calculator-container button:hover {
background-color: #0056b3;
}
.result-container {
margin-top: 20px;
padding: 15px;
border: 1px solid #d4edda;
background-color: #e9f7ef;
color: #155724;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
}
function calculateMortgageAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTermYears").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var resultDiv = document.getElementById("result");
// Input validation
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0 ||
isNaN(monthlyDebtPayments) || monthlyDebtPayments < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTermYears) || loanTermYears <= 0 ||
isNaN(downPayment) || downPayment < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Lender typically allows PITI (Principal, Interest, Taxes, Insurance) to be
// around 28-36% of gross monthly income. We'll use 30% as a common guideline.
var maxMonthlyPaymentAllowed = grossMonthlyIncome * 0.30;
// Subtract existing debt payments to find the maximum amount for the mortgage P&I
var maxMortgagePAndIPayment = maxMonthlyPaymentAllowed – monthlyDebtPayments;
// Ensure the max mortgage payment is not negative
if (maxMortgagePAndIPayment 0 && numberOfPayments > 0) {
var factor = Math.pow(1 + monthlyInterestRate, numberOfPayments);
var principalFactor = factor / (factor – 1);
maxLoanAmount = maxMortgagePAndIPayment * (1 / monthlyInterestRate) * (factor – 1) / factor;
} else if (maxMortgagePAndIPayment > 0) {
// Handle case where interest rate is 0 (unlikely for mortgage but for calculation integrity)
maxLoanAmount = maxMortgagePAndIPayment * numberOfPayments;
}
var estimatedMaxHomePrice = maxLoanAmount + downPayment;
// Display results
resultDiv.innerHTML = "Based on your input, you may be able to afford a home priced around:$" + estimatedMaxHomePrice.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "" +
"This includes your down payment of $" + downPayment.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "." +
"Your estimated maximum loan amount is: $" + maxLoanAmount.toFixed(2).replace(/\d(?=(\d{3})+\.)/g, '$&,') + "";
}
Understanding Mortgage Affordability
Determining how much house you can afford is a crucial step in the home-buying process. It's not just about what a lender might approve you for, but also about what you feel comfortable paying each month without straining your finances. This mortgage affordability calculator uses common lending guidelines to give you an estimate.
Key Factors Influencing Affordability:
Gross Monthly Income: This is your total income before taxes and other deductions. Lenders use this as a primary measure of your ability to repay a loan.
Existing Monthly Debt Payments: This includes payments for car loans, student loans, credit cards, personal loans, and any other recurring debts. These debts reduce the amount of income available for a mortgage.
Interest Rate: A lower interest rate means a lower monthly payment for the same loan amount, allowing you to borrow more or have a lower payment. Mortgage rates fluctuate based on market conditions and your creditworthiness.
Loan Term: This is the length of time you have to repay the mortgage, typically 15 or 30 years. A shorter loan term usually means higher monthly payments but less total interest paid over the life of the loan.
Down Payment: The amount of money you pay upfront towards the purchase price. A larger down payment reduces the loan amount needed and can sometimes lead to better interest rates or avoid private mortgage insurance (PMI).
Debt-to-Income Ratio (DTI): Lenders often look at your DTI, which is the percentage of your gross monthly income that goes towards paying your monthly debt obligations, including the estimated mortgage payment. A common guideline is that your total housing costs (Principal, Interest, Taxes, and Insurance – PITI) should not exceed 28% of your gross monthly income, and your total debt (including PITI) should not exceed 36%. Our calculator uses a simplified 30% of gross income for P&I + existing debts.
Important Note: This calculator provides an estimate only. It does not include property taxes, homeowners insurance, or potential private mortgage insurance (PMI), which are also part of your total monthly housing cost (PITI). Actual loan approval depends on a variety of factors, including your credit score, employment history, and the lender's specific underwriting criteria.