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 be able to borrow based on your income, debts, and desired monthly payment. It considers factors like your gross monthly income, existing monthly debt payments, and the estimated interest rate and loan term.
How it works: The calculator uses a common guideline where lenders typically want your total debt payments (including the potential mortgage payment) to not exceed a certain percentage of your gross monthly income. For example, a common benchmark is the "28/36 rule," where your housing expenses (PITI – Principal, Interest, Taxes, Insurance) shouldn't be more than 28% of your gross monthly income, and your total debt (including housing) shouldn't exceed 36% of your gross monthly income. Our calculator focuses on estimating the maximum loan amount based on a desired maximum monthly PITI payment, which is a key component of affordability.
Factors to consider:
Gross Monthly Income: This is your income before taxes and other deductions.
Existing Monthly Debt Payments: This includes credit card minimum payments, auto loans, student loans, personal loans, and any other recurring debt obligations.
Estimated Interest Rate: The annual interest rate you expect to pay on the mortgage. This can vary based on your credit score, the current market, and loan type.
Loan Term: The length of the mortgage, typically 15 or 30 years.
Down Payment: While not directly used in this loan amount calculator, your down payment significantly impacts the total home price you can afford and your monthly payments.
Property Taxes and Homeowners Insurance: These are crucial components of your monthly housing payment (PITI) and can vary significantly by location and property type.
Use this calculator as a guide to understand your borrowing potential. It's always recommended to speak with a mortgage lender for a pre-approval to get a precise figure.
Mortgage Affordability Calculator
15 Years
30 Years
function calculateMortgageAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var existingMonthlyDebt = parseFloat(document.getElementById("existingMonthlyDebt").value);
var maxMonthlyPITI = parseFloat(document.getElementById("maxMonthlyPITI").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseInt(document.getElementById("loanTerm").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(grossMonthlyIncome) || isNaN(existingMonthlyDebt) || isNaN(maxMonthlyPITI) || isNaN(interestRate) || isNaN(loanTerm)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (grossMonthlyIncome <= 0 || existingMonthlyDebt < 0 || maxMonthlyPITI <= 0 || interestRate < 0 || loanTerm 0) {
loanAmount = maxMonthlyPITI * (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments));
} else { // Handle zero interest rate scenario (though rare for mortgages)
loanAmount = maxMonthlyPITI * numberOfPayments;
}
// Simple check based on income guidelines (e.g., 28% of gross for housing)
var maxAffordablePITIByIncome = grossMonthlyIncome * 0.28;
var suggestedMaxLoanAmountBasedOnIncome = 0;
if (maxAffordablePITIByIncome > 0 && monthlyInterestRate > 0) {
suggestedMaxLoanAmountBasedOnIncome = maxAffordablePITIByIncome * (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments));
} else if (maxAffordablePITIByIncome > 0) {
suggestedMaxLoanAmountBasedOnIncome = maxAffordablePITIByIncome * numberOfPayments;
}
var totalMaxDebtAllowed = grossMonthlyIncome * 0.36;
var maxRemainingDebtForMortgage = totalMaxDebtAllowed – existingMonthlyDebt;
if (maxRemainingDebtForMortgage 0) {
if (monthlyInterestRate > 0) {
affordabilityLimitBasedOnTotalDebt = maxRemainingDebtForMortgage * (Math.pow(1 + monthlyInterestRate, numberOfPayments) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfPayments));
} else {
affordabilityLimitBasedOnTotalDebt = maxRemainingDebtForMortgage * numberOfPayments;
}
}
var finalLoanAmount = Math.min(loanAmount, suggestedMaxLoanAmountBasedOnIncome, affordabilityLimitBasedOnTotalDebt);
if (finalLoanAmount < 0) finalLoanAmount = 0; // Ensure no negative loan amount
resultDiv.innerHTML += "
Estimated Maximum Mortgage Loan Amount:
";
resultDiv.innerHTML += "$" + finalLoanAmount.toFixed(2) + "";
resultDiv.innerHTML += "Note: This is an estimate. Your actual borrowing capacity may vary. Factors like credit score, down payment, lender policies, and specific loan programs will influence the final loan amount.";
}