Mortgage Affordability Calculator
Use this calculator to estimate how much house you can afford 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;
}
.calculator-container h2 {
text-align: center;
margin-bottom: 15px;
color: #333;
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margin-bottom: 25px;
color: #555;
font-size: 0.95em;
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.calculator-form .form-group {
margin-bottom: 15px;
display: flex;
flex-direction: column;
}
.calculator-form label {
margin-bottom: 5px;
font-weight: bold;
color: #444;
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.calculator-form input[type="number"] {
padding: 10px;
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border-radius: 4px;
font-size: 1em;
box-sizing: border-box; /* Important */
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.calculator-form button {
width: 100%;
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transition: background-color 0.3s ease;
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.calculator-form button:hover {
background-color: #45a049;
}
.calculator-result {
margin-top: 20px;
padding: 15px;
background-color: #e7f3fe;
border: 1px solid #b3d4fc;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
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.calculator-result strong {
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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) / 100; // Convert percentage to decimal
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var maxPaymentPercentage = parseFloat(document.getElementById("maxPaymentPercentage").value) / 100; // Convert percentage to decimal
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(annualIncome) || annualIncome <= 0 ||
isNaN(monthlyDebt) || monthlyDebt < 0 ||
isNaN(downPayment) || downPayment < 0 ||
isNaN(interestRate) || interestRate < 0 ||
isNaN(loanTerm) || loanTerm <= 0 ||
isNaN(maxPaymentPercentage) || maxPaymentPercentage 1) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
var monthlyIncome = annualIncome / 12;
var maxPitiPayment = monthlyIncome * maxPaymentPercentage;
var maxMortgagePayment = maxPitiPayment – monthlyDebt;
if (maxMortgagePayment 0) { // Avoid division by zero if interest rate is 0
var numerator = Math.pow(1 + r, n) – 1;
var denominator = r * Math.pow(1 + r, n);
maxLoanAmount = maxMortgagePayment * (numerator / denominator);
} else { // If interest rate is 0, the loan amount is simply maxMortgagePayment * n
maxLoanAmount = maxMortgagePayment * n;
}
// Calculate estimated maximum home price
var maxHomePrice = maxLoanAmount + downPayment;
// Format results
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxHomePrice = maxHomePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxPiti = maxPitiPayment.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMonthlyDebt = monthlyDebt.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMonthlyIncome = monthlyIncome.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
resultDiv.innerHTML =
"Based on your inputs:" +
"Maximum estimated PITI payment:
" + formattedMaxPiti + " per month" +
"Available for mortgage (P&I) after debts:
" + (maxMortgagePayment > 0 ? maxMortgagePayment.toLocaleString(undefined, { style: 'currency', currency: 'USD' }) : "$0.00") + " per month" +
"Estimated maximum loan amount:
" + formattedMaxLoanAmount + "" +
"Estimated maximum affordable home price (with down payment):
" + formattedMaxHomePrice + "" +
"
Note: This is an estimate. Actual affordability depends on lender approval, credit score, property taxes, homeowner's insurance, and other factors.";
}
Understanding Mortgage Affordability
Determining how much house you can afford is a crucial step in the home-buying process. It's not just about what a lender might offer; it's about finding a home that fits comfortably within your budget and lifestyle. Several factors contribute to mortgage affordability, and this calculator helps you estimate a key component: how much you can borrow based on your income and existing debts.
Key Factors in Mortgage Affordability:
- Annual Gross Income: This is your total income before taxes and other deductions. Lenders look at this to gauge your ability to repay the loan.
- Total Monthly Debt Payments: This includes payments for credit cards, auto loans, student loans, personal loans, and any other recurring debts. These are subtracted from your potential housing payment to determine how much is left for a mortgage.
- Down Payment: The upfront cash you pay towards the home purchase. A larger down payment reduces the loan amount needed, making the purchase more affordable and potentially securing better loan terms.
- Interest Rate: The percentage charged by the lender on the loan amount. Even small differences in interest rates can significantly impact your monthly payment and the total interest paid over the life of the loan.
- Loan Term: The duration of the mortgage, typically 15 or 30 years. Shorter terms mean higher monthly payments but less interest paid overall.
- Maximum PITI Percentage: PITI stands for Principal, Interest, Taxes, and Insurance. Many lenders and financial advisors suggest that your total monthly PITI payment should not exceed a certain percentage (often 28%-36%) of your gross monthly income. This calculator uses a user-defined percentage to estimate your maximum affordable PITI.
How the Calculator Works:
This calculator takes your annual income and calculates your gross monthly income. It then determines the maximum monthly payment you're comfortable with for PITI, based on the percentage you set. From this maximum PITI, it subtracts your existing monthly debt payments to find out how much is available for the principal and interest (P&I) portion of your mortgage.
Using standard mortgage formulas, it then calculates the maximum loan amount you can afford with that P&I payment, given your chosen interest rate and loan term. Finally, it adds your down payment to this maximum loan amount to estimate the maximum home price you could potentially afford.
Example Calculation:
Let's say you have:
- Annual Gross Income: $90,000
- Total Monthly Debt Payments: $400 (e.g., car payment, credit card minimums)
- Down Payment: $25,000
- Estimated Annual Interest Rate: 6.8%
- Loan Term: 30 Years
- Maximum % of Income for PITI: 30%
Here's how the calculator would process this:
- Monthly Gross Income: $90,000 / 12 = $7,500
- Maximum PITI Payment: $7,500 * 0.30 = $2,250
- Available for Mortgage P&I: $2,250 (Max PITI) – $400 (Monthly Debts) = $1,850
- Using the mortgage formula with these figures, an interest rate of 6.8% over 30 years, the calculator estimates a maximum loan amount of approximately $276,000.
- Estimated Maximum Affordable Home Price: $276,000 (Loan Amount) + $25,000 (Down Payment) = $301,000
Remember, this is an estimate. Your actual borrowing power will be determined by a lender after a full review of your finances.