Understanding how much you can afford for a mortgage is a crucial first step in the home-buying process. This Mortgage Affordability Calculator helps you estimate the maximum loan amount you might qualify for, based on your income, debts, and other financial factors. It's important to remember that this calculator provides an estimate, and your actual loan approval will depend on a lender's specific underwriting criteria, including credit score, down payment, and market conditions.
How Mortgage Affordability Works
Lenders typically assess your ability to repay a loan by looking at your debt-to-income ratio (DTI). There are generally two types of DTI ratios considered:
Front-end DTI (Housing Ratio): This ratio compares your potential monthly housing costs (principal, interest, property taxes, homeowner's insurance, and potentially HOA fees) to your gross monthly income. A common guideline is to keep this below 28%.
Back-end DTI (Total Debt Ratio): This ratio compares all your monthly debt obligations (including potential housing costs, car payments, student loans, credit card minimum payments, etc.) to your gross monthly income. A common guideline is to keep this below 36%, though some lenders may allow up to 43% or even higher for certain loan programs.
Our calculator focuses on estimating the maximum loan amount based on these DTI principles, giving you a general idea of your borrowing power.
Factors Affecting Affordability
Gross Monthly Income: The total income you earn before taxes and other deductions.
Existing Monthly Debt Payments: This includes minimum payments for credit cards, car loans, student loans, personal loans, and any other recurring debts.
Estimated Monthly Property Taxes: The annual property taxes divided by 12.
Estimated Monthly Homeowner's Insurance: The annual homeowner's insurance premium divided by 12.
Estimated Monthly HOA Fees (if applicable): Monthly fees for homeowners association dues.
Interest Rate: The annual interest rate on the mortgage loan.
Loan Term: The length of the mortgage, typically 15 or 30 years.
Down Payment: The amount of money you pay upfront.
Use this calculator as a starting point to understand your potential mortgage affordability. For precise figures and loan qualification, consult with a mortgage lender.
Mortgage Affordability Calculator
30 Years
15 Years
Your Estimated Maximum Mortgage Amount:
$0.00
Note: This is an estimate. Actual loan amounts may vary.
function calculateMortgageAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var existingMonthlyDebt = parseFloat(document.getElementById("existingMonthlyDebt").value);
var propertyTaxesAnnual = parseFloat(document.getElementById("propertyTaxesAnnual").value);
var homeownersInsuranceAnnual = parseFloat(document.getElementById("homeownersInsuranceAnnual").value);
var hoaFeesMonthly = parseFloat(document.getElementById("hoaFeesMonthly").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var propertyTaxesMonthly = propertyTaxesAnnual / 12;
var homeownersInsuranceMonthly = homeownersInsuranceAnnual / 12;
// Define maximum DTI ratios (common guidelines)
var maxFrontEndDTIRatio = 0.28; // Housing ratio
var maxBackEndDTIRatio = 0.36; // Total debt ratio
// Ensure inputs are valid numbers
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0 ||
isNaN(existingMonthlyDebt) || existingMonthlyDebt < 0 ||
isNaN(propertyTaxesAnnual) || propertyTaxesAnnual < 0 ||
isNaN(homeownersInsuranceAnnual) || homeownersInsuranceAnnual < 0 ||
isNaN(hoaFeesMonthly) || hoaFeesMonthly < 0 ||
isNaN(interestRate) || interestRate <= 0 ||
isNaN(loanTermYears) || loanTermYears <= 0 ||
isNaN(downPayment) || downPayment 0 && monthlyInterestRate > 0) {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments);
maxLoanAmount = maxPrincipalInterestPayment * (numerator / denominator);
} else if (maxPrincipalInterestPayment <= 0) {
maxLoanAmount = 0; // If housing costs exceed income, no loan is possible
}
// Adjust for down payment to get the *maximum home price* affordability
// The calculator is asked to provide max LOAN amount, so we don't subtract down payment from total
// The calculated 'maxLoanAmount' is the maximum principal the borrower can afford.
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString('en-US', { style: 'currency', currency: 'USD' });
document.getElementById("maxLoanAmountResult").textContent = formattedMaxLoanAmount;
}