This calculator helps you estimate how much you can borrow for a mortgage based on your income, debts, and desired monthly payment.
.calculator-container {
font-family: Arial, sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
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text-align: center;
color: #333;
margin-bottom: 15px;
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.calculator-container p {
text-align: center;
color: #555;
margin-bottom: 25px;
line-height: 1.6;
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.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
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.input-group {
display: flex;
flex-direction: column;
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.input-group label {
margin-bottom: 5px;
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color: #444;
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.input-group input {
padding: 10px;
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cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 10px;
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.calculator-container button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 25px;
padding: 15px;
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text-align: center;
font-size: 1.1rem;
color: #0056b3;
min-height: 50px; /* Ensure it has some height even when empty */
display: flex;
align-items: center;
justify-content: center;
}
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 maxMonthlyPayment = parseFloat(document.getElementById("maxMonthlyPayment").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(annualIncome) || annualIncome <= 0 ||
isNaN(existingDebts) || existingDebts < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTerm) || loanTerm <= 0 ||
isNaN(maxMonthlyPayment) || maxMonthlyPayment 0 && numberOfMonths > 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths);
maxLoanAmount = affordableMonthlyPAndI * (numerator / denominator);
}
// However, we also need to ensure that the total debt payments (existing debts + mortgage P&I) don't exceed the 36% rule.
// This means our actual P&I payment might be limited by the total debt ratio.
var maxPAndIBasedOnTotalDebt = maxTotalDebtPayment – existingDebts;
// The final affordable monthly P&I payment is the minimum of the desired payment, the 28% rule, and the 36% total debt rule.
var finalAffordableMonthlyPAndI = Math.min(affordableMonthlyPAndI, maxPAndIBasedOnTotalDebt);
// Recalculate max loan amount if the payment was further constrained by the 36% rule.
if (finalAffordableMonthlyPAndI 0 && numberOfMonths > 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths);
maxLoanAmount = finalAffordableMonthlyPAndI * (numerator / denominator);
} else if (finalAffordableMonthlyPAndI < affordableMonthlyPAndI && monthlyInterestRate == 0){
// Handle zero interest rate case if needed, though uncommon for mortgages
maxLoanAmount = finalAffordableMonthlyPAndI * numberOfMonths;
}
// The maximum home price is the loan amount plus the down payment.
var maxHomePrice = maxLoanAmount + downPayment;
// Format results for display
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxHomePrice = maxHomePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedFinalMonthlyPAndI = finalAffordableMonthlyPAndI.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
resultDiv.innerHTML = "Based on your inputs, you might be able to afford a loan of approximately " +
formattedMaxLoanAmount +
". This suggests a maximum home price of around " +
formattedMaxHomePrice +
". Your estimated maximum Principal & Interest (P&I) monthly payment would be " +
formattedFinalMonthlyPAndI +
"." +
"Note: This is an estimation and does not include property taxes, homeowner's insurance, or potential Private Mortgage Insurance (PMI). Lender approval depends on many factors.";
}
Understanding Mortgage Affordability
Determining how much you can borrow for a home is a crucial step in the home-buying process. Mortgage affordability isn't just about finding the lowest interest rate; it's about understanding how much you can realistically and comfortably afford to pay each month, considering your income, existing financial obligations, and future financial goals.
Key Factors Influencing Affordability
Several components dictate how much a lender will approve you for, and more importantly, how much you should feel comfortable spending:
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 Debt Payments: This includes all recurring monthly payments for debts such as car loans, student loans, credit card minimum payments, and personal loans. Lenders assess your debt-to-income ratio (DTI) to understand your existing financial commitments.
Down Payment: The upfront cash you pay towards the purchase price of the home. A larger down payment reduces the loan amount needed, potentially making a home more affordable and often leading to better loan terms.
Interest Rate: The percentage charged by the lender for borrowing money. Even a small difference in interest rate can significantly impact your monthly payment and the total cost of the loan over time.
Loan Term: The duration over which you'll repay the loan, typically 15, 20, or 30 years. Shorter loan terms usually have higher monthly payments but less interest paid overall.
Property Taxes and Homeowner's Insurance (PITI): While this calculator focuses on Principal and Interest (P&I), remember that your actual monthly housing cost (PITI) will be higher. Lenders often use a front-end ratio (housing costs < 28% of gross monthly income) and a back-end ratio (total debt < 36% of gross monthly income) to assess affordability.
How the Calculator Works
Our Mortgage Affordability Calculator uses common lending guidelines to provide an estimate:
28% Rule: It estimates the maximum monthly Principal & Interest (P&I) payment you can afford, typically capping it at 28% of your gross monthly income.
36% Rule: It also considers your existing monthly debt payments. Your total monthly debt payments (including the estimated mortgage P&I) should ideally not exceed 36% of your gross monthly income. The calculator ensures your P&I payment doesn't push your total debt over this limit.
Desired Maximum Payment: You can input your personal maximum desired monthly payment, which acts as an additional ceiling. The calculator will use the lowest of these limits to determine your affordable P&I payment.
Loan Amount Calculation: Using the determined affordable monthly P&I payment, interest rate, and loan term, the calculator then computes the maximum loan amount you could qualify for.
Maximum Home Price: Finally, it adds your specified down payment to the maximum loan amount to estimate the maximum home price you might be able to afford.
Important Considerations
This calculator provides a valuable starting point, but it's essential to remember that it's an estimate. Lenders consider many other factors, including your credit score, employment history, assets, and the specific loan program. Always consult with a mortgage professional to get a pre-approval and a precise understanding of your borrowing capacity.