.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;
margin-bottom: 20px;
color: #333;
}
.calculator-inputs {
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;
box-sizing: border-box; /* Ensure padding doesn't affect width */
}
.calculator-container button {
background-color: #4CAF50;
color: white;
padding: 12px 20px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
width: 100%;
margin-top: 10px;
}
.calculator-container button:hover {
background-color: #45a049;
}
#result {
margin-top: 20px;
padding: 15px;
border: 1px solid #ddd;
background-color: #e9e9e9;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
#result span {
font-weight: bold;
color: #d9534f; /* Reddish for emphasis */
}
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var annualInterestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxRate = parseFloat(document.getElementById("propertyTaxRate").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var pmiRate = parseFloat(document.getElementById("pmiRate").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(annualIncome) || isNaN(monthlyDebt) || isNaN(downPayment) || isNaN(annualInterestRate) || isNaN(loanTerm) || isNaN(propertyTaxRate) || isNaN(homeInsurance) || isNaN(pmiRate)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (annualIncome <= 0 || monthlyDebt < 0 || downPayment < 0 || annualInterestRate <= 0 || loanTerm <= 0 || propertyTaxRate < 0 || homeInsurance < 0 || pmiRate < 0) {
resultDiv.innerHTML = "Please enter positive values for income, interest rate, and loan term. Debt, down payment, taxes, insurance, and PMI can be zero but not negative.";
return;
}
// DTI Ratio Calculation (Debt-to-Income)
// Lenders typically use a maximum DTI ratio (e.g., 36% for front-end, 43% for back-end).
// We'll use a common guideline of max 43% of gross income for total housing costs + debt.
var maxTotalMonthlyPayment = annualIncome * 0.43;
var maxHousingPayment = maxTotalMonthlyPayment – monthlyDebt;
if (maxHousingPayment <= 0) {
resultDiv.innerHTML = "Based on your income and existing debt, you may not qualify for a mortgage at this time. Consider reducing debt or increasing income.";
return;
}
// Mortgage Payment Calculation (P+I)
var monthlyInterestRate = (annualInterestRate / 100) / 12;
var numberOfMonths = loanTerm * 12;
var principalLoanAmount = 0; // We need to solve for this
var monthlyPmi = 0;
var monthlyPropertyTax = (annualIncome * (propertyTaxRate / 100)) / 12; // Property tax is often based on home value, but as a proxy for affordability we'll relate it to income. This is a simplification.
var monthlyHomeInsurance = homeInsurance / 12;
var maxLoanAmount = 0; // This is what we are solving for.
var step = 10000; // Increment for searching for the max loan amount
var maxPossibleLoanAmount = annualIncome * 10; // A very rough upper bound
// Iterative approach to find the maximum loan amount
for (var loanAmountGuess = 0; loanAmountGuess 0) {
currentMonthlyMortgagePayment = loanAmountGuess * (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths)) / (Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1);
} else {
// Handle zero interest rate case
currentMonthlyMortgagePayment = loanAmountGuess / numberOfMonths;
}
// Calculate PMI if applicable (often required for 0 ? loanAmountGuess / (loanAmountGuess + downPayment) : 0; // Crude LTV proxy
if (loanToValueRatio > 0.80 || downPayment 80% or down payment is less than 20% of total value
currentPmi = loanAmountGuess * (pmiRate / 100) / 12;
}
var totalMonthlyHousingCost = currentMonthlyMortgagePayment + monthlyPropertyTax + monthlyHomeInsurance + currentPmi;
if (totalMonthlyHousingCost > maxHousingPayment) {
maxLoanAmount = loanAmountGuess – step; // The previous step was affordable
break;
}
maxLoanAmount = loanAmountGuess; // If loop finishes, this is the max we could afford
}
var affordableHomePrice = maxLoanAmount + downPayment;
// Format results
var formattedAffordableHomePrice = affordableHomePrice.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
var formattedMaxHousingPayment = maxHousingPayment.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
resultDiv.innerHTML = `
Your estimated maximum affordable home price is: ${formattedAffordableHomePrice}
This includes your down payment of ${downPayment.toLocaleString('en-US', { style: 'currency', currency: 'USD' })}.
The maximum loan amount you might qualify for is: ${formattedMaxLoanAmount}
Your estimated maximum total monthly housing payment (PITI + PMI) is: ${formattedMaxHousingPayment}
`;
}
Understanding Mortgage Affordability
Determining how much house you can afford is a crucial first step in the home-buying process. It's not just about the loan amount; it involves a complex interplay of your income, existing debts, the cost of the home, and ongoing property expenses. This calculator helps estimate your maximum affordable home price by considering several key factors.
Key Factors Explained:
Annual Income: This is your gross income before taxes. Lenders use this to determine your borrowing capacity.
Existing Monthly Debt Payments: This includes payments for credit cards, car loans, student loans, and any other recurring debts. These are subtracted from your income to find the amount available for a mortgage.
Down Payment: The amount of cash you can put down upfront towards the purchase price. A larger down payment reduces the loan amount needed and can improve your loan terms.
Estimated Annual Interest Rate: The annual interest rate you expect to pay on your mortgage. This significantly impacts your monthly payments.
Loan Term (Years): The length of time over which you will repay the mortgage (e.g., 15, 20, or 30 years). Longer terms result in lower monthly payments but more interest paid overall.
Annual Property Tax Rate: The yearly property taxes, usually expressed as a percentage of the home's value. These are typically paid monthly as part of your mortgage payment (escrow).
Annual Homeowners Insurance: The cost of insuring your home against damage or loss. This is also usually paid monthly via escrow.
Annual Private Mortgage Insurance (PMI) Rate: If your down payment is less than 20% of the home's value, lenders often require PMI to protect themselves. This is an additional monthly cost.
How the Calculator Works:
This calculator uses a common guideline where your total monthly housing expenses (Principal, Interest, Taxes, Insurance, plus PMI) should not exceed a certain percentage of your gross monthly income, typically around 43% (this is known as the back-end Debt-to-Income ratio or DTI). It also accounts for your existing monthly debt obligations.
The calculator first determines the maximum amount you can allocate towards a monthly mortgage payment after covering your existing debts. It then iteratively calculates the largest loan amount that would result in a total monthly housing cost within your affordable limit, considering the interest rate, loan term, property taxes, homeowners insurance, and PMI. Finally, it adds your down payment to this maximum loan amount to estimate your affordable home price.
Disclaimer: This calculator provides an estimate for informational purposes only. It does not constitute financial advice. Actual loan approval and affordability depend on many factors, including lender-specific underwriting criteria, your credit score, employment history, and current market conditions. It is highly recommended to consult with a mortgage professional for personalized advice.