Understanding how much mortgage you can afford is a crucial step in the home-buying process.
This calculator helps you estimate your maximum affordable mortgage amount by considering your
income, debts, and desired monthly payment. It's important to remember that this is an
estimate, and your actual loan approval will depend on factors like your credit score,
down payment, lender policies, and current market conditions.
Your Estimated Maximum Mortgage Affordability:
How Mortgage Affordability is Calculated
Lenders typically use debt-to-income ratios (DTI) to assess your ability to repay a loan.
There are generally two DTI thresholds they consider:
Front-end DTI (Housing Ratio): This ratio looks at your proposed housing costs (principal, interest, taxes, and insurance – PITI) as a percentage of your gross monthly income. Many lenders prefer this to be no more than 28%.
Back-end DTI (Total Debt Ratio): This ratio includes all your monthly debt obligations (proposed housing costs plus existing debts like car loans, student loans, and credit card minimum payments) as a percentage of your gross monthly income. Lenders often prefer this to be no more than 36%, though some may go up to 43% or higher depending on other factors.
This calculator uses a simplified approach that focuses on your maximum comfortable monthly payment,
considering your income and existing debts. It then estimates the loan amount you could afford
based on that payment and the given interest rate and loan term.
Factors Influencing Affordability:
Credit Score: A higher credit score usually leads to lower interest rates, increasing your affordability.
Down Payment: A larger down payment reduces the loan amount needed, making the mortgage more affordable and potentially lowering your interest rate.
Closing Costs: Don't forget to factor in closing costs, which are additional expenses associated with finalizing a mortgage.
Property Taxes and Homeowner's Insurance: These costs (often included in PITI) can vary significantly by location and property type.
Private Mortgage Insurance (PMI): If your down payment is less than 20%, you'll likely need to pay PMI, which adds to your monthly housing cost.
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var resultElement = document.getElementById("result");
var maxMortgageAmountElement = document.getElementById("maxMortgageAmount");
var estimatedMaxHomePriceElement = document.getElementById("estimatedMaxHomePrice");
if (isNaN(annualIncome) || isNaN(monthlyDebtPayments) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || annualIncome <= 0 || monthlyDebtPayments < 0 || downPayment < 0 || interestRate <= 0 || loanTerm <= 0) {
resultElement.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
var monthlyIncome = annualIncome / 12;
// A common guideline is that total housing costs (PITI) should not exceed 28% of gross monthly income.
// We'll use this as a basis for maximum monthly housing payment.
var maxMonthlyHousingPayment = monthlyIncome * 0.28;
// Subtract existing monthly debts from the maximum affordable housing payment to find the maximum P&I payment.
var maxPrincipalInterestPayment = maxMonthlyHousingPayment – monthlyDebtPayments;
// Ensure the maximum principal and interest payment is not negative.
if (maxPrincipalInterestPayment 0 && numberOfPayments > 0) {
// Formula for present value of an annuity (loan amount)
maxMortgageLoan = maxPrincipalInterestPayment * (1 – Math.pow(1 + monthlyInterestRate, -numberOfPayments)) / monthlyInterestRate;
} else if (monthlyInterestRate === 0 && numberOfPayments > 0) {
// Special case for 0 interest rate
maxMortgageLoan = maxPrincipalInterestPayment * numberOfPayments;
}
// Round to two decimal places for currency
var formattedMaxMortgageLoan = maxMortgageLoan.toFixed(2);
// Estimate the maximum home price by adding the down payment
var estimatedMaxHomePrice = maxMortgageLoan + downPayment;
var formattedMaxHomePrice = estimatedMaxHomePrice.toFixed(2);
maxMortgageAmountElement.innerHTML = "Maximum Loan Amount: $" + parseFloat(formattedMaxMortgageLoan).toLocaleString(undefined, { minimumFractionDigits: 2, maximumFractionDigits: 2 });
estimatedMaxHomePriceElement.innerHTML = "Estimated Maximum Home Price: $" + parseFloat(formattedMaxHomePrice).toLocaleString(undefined, { minimumFractionDigits: 2, maximumFractionDigits: 2 });
}