.calculator-container {
font-family: sans-serif;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
margin-bottom: 20px;
color: #333;
}
.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: #555;
}
.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;
}
button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
.calculator-result strong {
color: #28a745;
}
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var existingDebts = parseFloat(document.getElementById("existingDebts").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxes = parseFloat(document.getElementById("propertyTaxes").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var hoaFees = parseFloat(document.getElementById("hoaFees").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(annualIncome) || isNaN(existingDebts) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(propertyTaxes) || isNaN(homeInsurance) || isNaN(hoaFees)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
// Rule of thumb: Lenders often use the 28/36 rule.
// Front-end ratio (PITI): Housing costs (Principal, Interest, Taxes, Insurance) should not exceed 28% of gross monthly income.
// Back-end ratio (DTI): Total debt payments (PITI + existing debts) should not exceed 36% of gross monthly income.
var grossMonthlyIncome = annualIncome / 12;
var maxHousingPayment = grossMonthlyIncome * 0.28;
var maxTotalDebtPayment = grossMonthlyIncome * 0.36;
// We need to estimate the maximum loan amount based on the *max housing payment*
// The housing payment consists of PITI (Principal, Interest, Taxes, Insurance) + HOA
// We'll iteratively try to find a loan amount that fits. This is complex to do precisely without an iterative solver.
// A simpler approach is to estimate the maximum *affordable monthly PITI payment* first.
var monthlyPropertyTaxes = propertyTaxes / 12;
var monthlyHomeInsurance = homeInsurance / 12;
var monthlyHoaFees = hoaFees; // Already monthly
var maxAffordablePITI = maxHousingPayment – monthlyPropertyTaxes – monthlyHomeInsurance – monthlyHoaFees;
if (maxAffordablePITI <= 0) {
resultDiv.innerHTML = "Your estimated housing costs (taxes, insurance, HOA) already exceed the recommended maximum housing payment. You may not qualify for a mortgage with these parameters.";
return;
}
// Now, let's try to calculate the maximum loan amount that would result in a PITI payment 0) {
var mortgageFactor = (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
maxLoanAmount = maxAffordablePITI / mortgageFactor;
} else {
// Handle 0 interest rate case (rare, but possible)
maxLoanAmount = maxAffordablePITI * numberOfPayments;
}
var estimatedMaxHomePrice = maxLoanAmount + downPayment;
// We also need to check the 36% DTI rule.
// Total monthly debt = PITI + existingDebts.
// We need to find the PITI portion of the loan.
// Let's calculate the actual estimated PITI payment for our calculated loan amount to verify.
var estimatedMonthlyPITI = 0;
if (monthlyInterestRate > 0) {
var mortgageFactor = (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments)) / (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1);
estimatedMonthlyPITI = maxLoanAmount * mortgageFactor;
} else {
estimatedMonthlyPITI = maxLoanAmount / numberOfPayments;
}
var totalEstimatedMonthlyExpenses = estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees + existingDebts;
var affordabilityMessage = "";
var passed28PercentRule = (estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees) <= maxHousingPayment;
var passed36PercentRule = totalEstimatedMonthlyExpenses <= maxTotalDebtPayment;
if (passed28PercentRule && passed36PercentRule) {
affordabilityMessage = "Based on the 28/36 rule and your inputs, you may be able to afford a home around the estimated price of $" + estimatedMaxHomePrice.toFixed(2) + ". This includes your down payment.";
affordabilityMessage += "Estimated Maximum Loan Amount: $" + maxLoanAmount.toFixed(2) + "";
affordabilityMessage += "Estimated Maximum Affordable Monthly PITI Payment: $" + (estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees).toFixed(2) + "";
} else if (passed28PercentRule) {
affordabilityMessage = "You meet the 28% housing expense rule, but your total debt payments (including estimated mortgage PITI) may exceed the 36% DTI limit. You might qualify for a slightly smaller loan or need to reduce existing debts.";
affordabilityMessage += "Estimated Maximum Affordable Monthly PITI Payment: $" + (estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees).toFixed(2) + "";
affordabilityMessage += "Estimated Total Monthly Debt Payments: $" + totalEstimatedMonthlyExpenses.toFixed(2) + " (Exceeds 36% DTI)";
} else if (passed36PercentRule) {
affordabilityMessage = "You meet the 36% total debt-to-income rule, but your estimated housing costs (PITI + taxes, insurance, HOA) may exceed the 28% guideline. You might qualify for a slightly smaller loan.";
affordabilityMessage += "Estimated Maximum Affordable Monthly PITI Payment: $" + (estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees).toFixed(2) + " (Exceeds 28% Housing)";
affordabilityMessage += "Estimated Total Monthly Debt Payments: $" + totalEstimatedMonthlyExpenses.toFixed(2) + "";
} else {
affordabilityMessage = "Based on the 28/36 rule, your current income and debt levels may not support a mortgage of the size implied by your inputs. Consider reducing existing debts or increasing your income/down payment.";
affordabilityMessage += "Estimated Maximum Affordable Monthly PITI Payment: $" + (estimatedMonthlyPITI + monthlyPropertyTaxes + monthlyHomeInsurance + monthlyHoaFees).toFixed(2) + " (Exceeds 28% Housing)";
affordabilityMessage += "Estimated Total Monthly Debt Payments: $" + totalEstimatedMonthlyExpenses.toFixed(2) + " (Exceeds 36% DTI)";
}
resultDiv.innerHTML = affordabilityMessage;
}
Understanding Mortgage Affordability
Buying a home is one of the biggest financial decisions you'll make. Determining how much you can realistically afford for a mortgage is crucial before you start house hunting. This calculator helps estimate your potential mortgage affordability by considering several key financial factors. It's important to remember that this is an estimation tool, and actual lender approvals may vary based on their specific underwriting criteria, credit scores, and market conditions.
Key Factors Influencing Your Affordability
Annual Household Income: This is the primary driver of your borrowing capacity. Lenders look at your gross income (before taxes) to assess how much you can afford to spend on housing.
Monthly Debt Payments: Existing financial obligations like car loans, student loans, personal loans, and credit card minimum payments reduce the amount of income available for a mortgage. Lenders use these to calculate your Debt-to-Income (DTI) ratio.
Down Payment: A larger down payment reduces the amount you need to borrow, which can lower your monthly payments and potentially help you avoid Private Mortgage Insurance (PMI).
Interest Rate: Even small changes in the interest rate can significantly impact your monthly payment and the total cost of your loan over time.
Loan Term: Mortgages are typically offered in terms of 15 or 30 years. Shorter terms mean higher monthly payments but less interest paid overall, while longer terms mean lower monthly payments but more interest paid over the life of the loan.
Property Taxes: These are annual taxes assessed by local governments on the value of your property. They are typically paid monthly as part of your mortgage payment (escrow).
Homeowners Insurance: This protects you financially against damage or loss to your home. It's also usually paid monthly through escrow.
HOA Fees: If you are buying a property in a community with a Homeowners Association, these monthly or annual fees cover the maintenance of common areas and amenities.
The 28/36 Rule (A Common Guideline)
Lenders often use the "28/36 rule" as a benchmark for determining mortgage affordability:
The 28% Rule (Front-End Ratio): Your total monthly housing costs, including principal, interest, property taxes, homeowners insurance, and any HOA fees (often referred to as PITI + HOA), should not exceed 28% of your gross monthly income.
The 36% Rule (Back-End Ratio): Your total monthly debt obligations, including your estimated PITI + HOA payments PLUS all other monthly debt payments (like car loans, student loans, credit cards), should not exceed 36% of your gross monthly income.
This calculator estimates your maximum loan amount based on the 28% rule and then checks if the total debt load (including that estimated mortgage payment) stays within the 36% rule. It provides an estimated maximum home price you might be able to afford.
$3,400 (Total Debt) is less than $3,600 (Max Total Debt), so they meet the 36% DTI rule.
In this scenario, the calculator would indicate they could potentially afford a home around $391,811.
Disclaimer
This calculator provides an estimate based on common lending guidelines. It does not take into account all factors that lenders consider, such as credit score, employment history, assets, or specific lender overlays. Always consult with a qualified mortgage professional for a pre-approval and personalized advice.