Determine your maximum purchasing power based on the 28/36 rule.
Max Home Price:–
Max Monthly Payment:–
Principal & Interest:–
Estimated Taxes & Insurance:–
Loan Amount:–
How Much House Can You Afford?
Determining your home buying budget is the most critical first step in the real estate journey. This Home Affordability Calculator uses standard lender guidelines to estimate your purchasing power, helping you search for homes that fit your financial comfort zone without overextending your budget.
Understanding the 28/36 Rule
Lenders typically use two debt-to-income (DTI) ratios to determine how much money they will lend you. This calculator applies these standard "front-end" and "back-end" ratios:
The Front-End Ratio (28%): Historically, lenders prefer that your total housing costs (mortgage principal, interest, taxes, and insurance) do not exceed 28% of your gross monthly income.
The Back-End Ratio (36%): Your total debt load—including your new housing costs plus existing debts like car loans, student loans, and credit cards—should typically not exceed 36% of your gross monthly income.
Key Factors Affecting Your Affordability
Several variables influence your maximum home price beyond just your salary:
Down Payment: A larger down payment reduces the loan amount required, allowing you to purchase a more expensive home for the same monthly payment. It may also help you avoid Private Mortgage Insurance (PMI).
Interest Rates: Even a small increase in interest rates can significantly reduce your purchasing power. As rates rise, the cost of borrowing increases, meaning you can afford less "house" for the same monthly payment.
Monthly Debts: Reducing your existing monthly obligations (like paying off a car note) directly increases the amount of income available for a mortgage, potentially boosting your budget significantly.
Property Taxes & Insurance: These recurring costs are included in your DTI calculation. Buying in an area with lower property taxes can increase the loan amount you qualify for.
How to Use This Calculator
Input your annual household income before taxes, your estimated monthly debt payments (do not include your current rent or mortgage), the cash you have saved for a down payment, and current market interest rates. The calculator will determine the maximum monthly payment lenders are likely to approve and reverse-calculate the total home price based on that figure.
function calculateAffordability() {
// Get Inputs
var annualIncome = parseFloat(document.getElementById('annualIncome').value);
var monthlyDebts = parseFloat(document.getElementById('monthlyDebts').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var interestRate = parseFloat(document.getElementById('interestRate').value);
var loanTerm = parseFloat(document.getElementById('loanTerm').value);
var propertyTax = parseFloat(document.getElementById('propertyTax').value);
var homeInsurance = parseFloat(document.getElementById('homeInsurance').value);
var hoaFees = parseFloat(document.getElementById('hoaFees').value);
// Validation
if (isNaN(annualIncome) || isNaN(interestRate) || isNaN(loanTerm)) {
alert("Please enter valid numbers for Income, Interest Rate, and Loan Term.");
return;
}
// Set defaults for optional fields if empty
if (isNaN(monthlyDebts)) monthlyDebts = 0;
if (isNaN(downPayment)) downPayment = 0;
if (isNaN(propertyTax)) propertyTax = 0;
if (isNaN(homeInsurance)) homeInsurance = 0;
if (isNaN(hoaFees)) hoaFees = 0;
// Calculate Monthly Gross Income
var monthlyIncome = annualIncome / 12;
// 1. Front-End Ratio Limit (Housing costs <= 28% of income)
var maxHousingFront = monthlyIncome * 0.28;
// 2. Back-End Ratio Limit (Total debt <= 36% of income)
// Max Housing = (Income * 0.36) – Other Debts
var maxHousingBack = (monthlyIncome * 0.36) – monthlyDebts;
// The limiting factor is the lower of the two
var maxAllowablePayment = Math.min(maxHousingFront, maxHousingBack);
// If debts are too high, maxHousingBack could be negative
if (maxAllowablePayment 0) {
// Reverse Mortgage Calculation to find Loan Amount
// Formula: P = M * [ (1+r)^n – 1 ] / [ r(1+r)^n ]
var monthlyRate = (interestRate / 100) / 12;
var numPayments = loanTerm * 12;
if (monthlyRate === 0) {
maxLoanAmount = maxPI * numPayments;
} else {
var factor = Math.pow(1 + monthlyRate, numPayments);
maxLoanAmount = maxPI * (factor – 1) / (monthlyRate * factor);
}
// Total Price = Loan + Down Payment
maxHomePrice = maxLoanAmount + downPayment;
} else {
maxPI = 0;
maxLoanAmount = 0;
maxHomePrice = downPayment; // Can only afford what they can pay cash for if debts are too high
}
// Display Results
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
maximumFractionDigits: 0
});
document.getElementById('maxHomePrice').innerText = formatter.format(maxHomePrice);
document.getElementById('maxMonthlyPayment').innerText = formatter.format(maxAllowablePayment);
document.getElementById('principalInterest').innerText = formatter.format(maxPI);
document.getElementById('taxInsurance').innerText = formatter.format(totalNonMortgage);
document.getElementById('loanAmountResult').innerText = formatter.format(maxLoanAmount);
// Show Results Div
document.getElementById('resultsArea').style.display = 'block';
}