Use this calculator to estimate how much you can afford to borrow for a mortgage based on your income and debts. This is a preliminary estimate and not a loan approval.
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 15px;
}
.calculator-container p {
text-align: center;
color: #555;
margin-bottom: 25px;
font-size: 0.95em;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
}
.input-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
margin-bottom: 20px;
}
button:hover {
background-color: #0056b3;
}
.calculator-result {
text-align: center;
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
font-size: 1.1em;
color: #333;
min-height: 50px;
display: flex;
justify-content: center;
align-items: center;
}
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Validate inputs
if (isNaN(annualIncome) || isNaN(monthlyDebt) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) ||
annualIncome <= 0 || monthlyDebt < 0 || downPayment < 0 || interestRate <= 0 || loanTerm <= 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Lender typically uses DTI ratios. Common thresholds are 28% for PITI and 36%-43% for total debt.
// We'll use a common guideline: PITI shouldn't exceed 28% of gross monthly income.
// Total debt (PITI + other debts) shouldn't exceed 36% of gross monthly income.
var grossMonthlyIncome = annualIncome / 12;
// Maximum allowed monthly housing payment (Principal, Interest, Taxes, Insurance – PITI)
var maxPitiPayment = grossMonthlyIncome * 0.28;
// Maximum allowed total monthly debt payments
var maxTotalMonthlyDebt = grossMonthlyIncome * 0.36;
// Maximum affordable monthly mortgage payment (excluding principal and interest, as we'll calculate that)
// This is the portion of maxTotalMonthlyDebt that can go towards the mortgage
var maxAffordablePrincipalInterest = maxTotalMonthlyDebt – monthlyDebt;
if (maxAffordablePrincipalInterest 0) {
// Formula for maximum loan amount based on a fixed monthly payment (M):
// L = M * [1 – (1 + r)^-n] / r
// where L is loan amount, M is monthly payment, r is monthly interest rate, n is number of payments
maxLoanAmount = maxPiPayment * (1 – Math.pow(1 + monthlyInterestRate, -numberOfPayments)) / monthlyInterestRate;
} else {
// If interest rate is 0 (rare, but for completeness)
maxLoanAmount = maxPiPayment * numberOfPayments;
}
// The maximum house price you can afford is the maximum loan amount plus your down payment.
var maxAffordableHousePrice = maxLoanAmount + downPayment;
// Format results
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxAffordableHousePrice = maxAffordableHousePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxPiPayment = maxPiPayment.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
resultDiv.innerHTML = "Estimated Maximum Loan Amount: " + formattedMaxLoanAmount +
"Estimated Maximum Affordable House Price: " + formattedMaxAffordableHousePrice +
"(Based on a maximum P&I payment of " + formattedMaxPiPayment + " per month)";
}