Understanding how much house you can afford is a crucial first step in the home-buying process. This calculator helps you estimate your potential mortgage affordability based on your income, debts, and down payment. Remember, this is an estimate, and your actual loan amount may vary based on lender requirements, credit score, and market conditions.
.calculator-container {
font-family: sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ccc;
border-radius: 8px;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calculator-form {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.form-group {
display: flex;
flex-direction: column;
}
.form-group label {
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.form-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
}
.calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1rem;
cursor: pointer;
transition: background-color 0.3s ease;
}
.calculator-container button:hover {
background-color: #0056b3;
}
#result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #dee2e6;
border-radius: 4px;
text-align: center;
font-size: 1.1rem;
color: #333;
}
#result strong {
color: #007bff;
}
function calculateMortgageAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var annualInterestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseFloat(document.getElementById("loanTerm").value);
var annualPropertyTaxes = parseFloat(document.getElementById("propertyTaxes").value);
var annualHomeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var annualPmi = parseFloat(document.getElementById("pmi").value);
var resultDiv = document.getElementById("result");
if (isNaN(grossMonthlyIncome) || isNaN(monthlyDebtPayments) || isNaN(downPayment) || isNaN(annualInterestRate) || isNaN(loanTermYears) || isNaN(annualPropertyTaxes) || isNaN(annualHomeInsurance) || isNaN(annualPmi)) {
resultDiv.innerHTML = "Error: Please enter valid numbers for all fields.";
return;
}
// Debt-to-Income (DTI) Ratio Calculation
// Lenders typically look for a DTI ratio below 43% (including housing costs)
var maxDtiRatio = 0.43;
var maxTotalMonthlyPayments = grossMonthlyIncome * maxDtiRatio;
var maxHousingPayment = maxTotalMonthlyPayments – monthlyDebtPayments;
if (maxHousingPayment < 0) {
resultDiv.innerHTML = "Sorry: Based on your income and debts, you may not qualify for a mortgage at this time. Your current debt payments exceed your affordable housing budget.";
return;
}
// Convert annual expenses to monthly
var monthlyPropertyTaxes = annualPropertyTaxes / 12;
var monthlyHomeInsurance = annualHomeInsurance / 12;
var monthlyPmi = annualPmi / 12;
// Calculate maximum affordable loan amount
// We need to work backward from the maximum monthly housing payment
// Max Housing Payment = Principal & Interest (P&I) + Taxes + Insurance + PMI
var monthlyPni = maxHousingPayment – monthlyPropertyTaxes – monthlyHomeInsurance – monthlyPmi;
if (monthlyPni <= 0) {
resultDiv.innerHTML = "Sorry: Your estimated monthly housing expenses (taxes, insurance, PMI) are too high for your income. You may need to adjust your budget or consider a less expensive home.";
return;
}
var monthlyInterestRate = (annualInterestRate / 100) / 12;
var loanTermMonths = loanTermYears * 12;
// Using the loan payment formula to solve for loan principal (P)
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1]
// P = M [ (1 + i)^n – 1] / [ i(1 + i)^n ]
var maxLoanAmount = 0;
if (monthlyInterestRate > 0) {
maxLoanAmount = monthlyPni * (Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTermMonths));
} else { // Handle 0% interest rate, though rare for mortgages
maxLoanAmount = monthlyPni * loanTermMonths;
}
// Maximum affordable home price = Max Loan Amount + Down Payment
var maxHomePrice = maxLoanAmount + downPayment;
// Display Results
resultDiv.innerHTML = "Estimated Maximum Home Price You Can Afford: $" + maxHomePrice.toFixed(2) + "" +
"Estimated Maximum Mortgage Loan Amount: $" + maxLoanAmount.toFixed(2) + "" +
"Estimated Maximum Monthly Housing Payment (PITI): $" + maxHousingPayment.toFixed(2) + "";
}