Please enter valid numbers for income and interest rate.
Affordability Results
Maximum Home Price:$0
Loan Amount:$0
Down Payment:$0
Max Monthly Payment (P&I + Taxes + Ins):$0
Based on DTI Ratio:0%
How Much House Can You Afford?
Determine your purchasing power with our specialized Mortgage Affordability Calculator. Unlike simple loan calculators, this tool considers your debt-to-income (DTI) ratio, which is the primary metric lenders use to approve mortgages. By inputting your income, existing debts, and estimated property costs, we calculate the maximum home price that fits within standard lending guidelines.
Understanding the 28/36 Rule
Most financial institutions follow the 28/36 rule to determine affordability:
Front-End Ratio (28%): Your monthly housing costs (principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income.
Back-End Ratio (36%): Your total monthly debt payments (housing costs plus credit cards, car loans, student loans, etc.) should not exceed 36% of your gross monthly income.
This calculator determines the maximum payment allowed under both rules and uses the lower (more conservative) figure to ensure you don't overextend your budget.
Factors That Impact Your Affordability
Several key variables change how much house you can buy:
Interest Rates: A higher interest rate increases your monthly payment, significantly reducing the loan amount you can afford for the same monthly budget.
Down Payment: A larger down payment reduces the loan amount needed and immediately increases your maximum purchase price dollar-for-dollar.
Monthly Debts: Reducing other monthly obligations (like paying off a car loan) lowers your back-end DTI ratio, potentially unlocking a higher mortgage budget.
Property Taxes & HOA: High taxes or Homeowner Association fees reduce the portion of your monthly payment available for the mortgage principal and interest, lowering your total purchasing power.
function calculateMortgageAffordability() {
// Get Inputs
var income = parseFloat(document.getElementById("annualIncome").value);
var debts = parseFloat(document.getElementById("monthlyDebts").value) || 0;
var downPayment = parseFloat(document.getElementById("downPayment").value) || 0;
var rate = parseFloat(document.getElementById("interestRate").value);
var years = parseFloat(document.getElementById("loanTerm").value);
var tax = parseFloat(document.getElementById("monthlyTax").value) || 0;
var insurance = parseFloat(document.getElementById("monthlyInsurance").value) || 0;
var hoa = parseFloat(document.getElementById("hoaFees").value) || 0;
var errorDiv = document.getElementById("macErrorMessage");
var resultDiv = document.getElementById("macResults");
// Basic Validation
if (isNaN(income) || isNaN(rate) || income <= 0 || rate <= 0) {
errorDiv.style.display = "block";
resultDiv.style.display = "none";
return;
}
errorDiv.style.display = "none";
// Monthly Income
var monthlyIncome = income / 12;
// Front-End Ratio Limit (28% of Income for Housing)
var limitFront = monthlyIncome * 0.28;
// Back-End Ratio Limit (36% of Income for Total Debt)
// Total Debt Allowed – Existing Debts = Allowed Housing Payment
var limitBack = (monthlyIncome * 0.36) – debts;
// The limiting factor is the lower of the two
var maxTotalHousingPayment = Math.min(limitFront, limitBack);
// Determine which rule limited the budget for display
var limitingRule = (limitFront 0) {
// Mortgage Formula: P = L[c(1 + c)^n]/[(1 + c)^n – 1]
// Reverse to find L: L = P * [(1 + c)^n – 1] / [c(1 + c)^n]
var monthlyRate = rate / 100 / 12;
var numPayments = years * 12;
// Calculate factor: (1+r)^n
var compoundFactor = Math.pow(1 + monthlyRate, numPayments);
// Calculate Loan Amount
maxLoanAmount = availableForPI * (compoundFactor – 1) / (monthlyRate * compoundFactor);
} else {
availableForPI = 0; // Cannot afford anything
}
// Max Home Price = Loan Amount + Down Payment
var maxHomePrice = maxLoanAmount + downPayment;
// Formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
maximumFractionDigits: 0
});
// Update UI
document.getElementById("resMaxHomePrice").innerHTML = formatter.format(maxHomePrice);
document.getElementById("resLoanAmount").innerHTML = formatter.format(maxLoanAmount);
document.getElementById("resDownPayment").innerHTML = formatter.format(downPayment);
document.getElementById("resMaxMonthly").innerHTML = formatter.format(maxTotalHousingPayment);
document.getElementById("resDTILimit").innerHTML = limitingRule;
resultDiv.style.display = "block";
}