.calc-header { background: #1a365d; color: #ffffff; padding: 30px 20px; text-align: center; }
.calc-header h2 { margin: 0; font-size: 28px; }
.calc-container { padding: 25px; }
.input-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-bottom: 25px; }
.input-group { margin-bottom: 15px; }
.input-group label { display: block; font-weight: 600; margin-bottom: 8px; font-size: 14px; color: #4a5568; }
.input-group input, .input-group select { width: 100%; padding: 12px; border: 2px solid #e2e8f0; border-radius: 6px; box-sizing: border-box; font-size: 16px; transition: border-color 0.2s; }
.input-group input:focus { border-color: #3182ce; outline: none; }
.calc-btn { width: 100%; background: #3182ce; color: #fff; border: none; padding: 15px; font-size: 18px; font-weight: 700; border-radius: 6px; cursor: pointer; transition: background 0.2s; margin-bottom: 25px; }
.calc-btn:hover { background: #2c5282; }
.results-box { background: #f7fafc; border: 2px solid #edf2f7; border-radius: 8px; padding: 20px; display: none; margin-bottom: 25px; }
.results-box h3 { margin-top: 0; color: #2d3748; text-align: center; border-bottom: 1px solid #e2e8f0; padding-bottom: 10px; }
.result-item { display: flex; justify-content: space-between; margin: 12px 0; font-size: 16px; }
.result-value { font-weight: 700; color: #2c5282; }
.result-highlight { font-size: 24px; color: #2f855a; }
.article-content { padding: 25px; background: #fff; border-top: 1px solid #eee; }
.article-content h3 { color: #1a365d; margin-top: 25px; }
@media (max-width: 600px) { .input-grid { grid-template-columns: 1fr; } }
function calculateMortgageAffordability() {
var annualIncome = parseFloat(document.getElementById('annualIncome').value);
var monthlyDebt = parseFloat(document.getElementById('monthlyDebt').value);
var downPayment = parseFloat(document.getElementById('downPayment').value);
var annualRate = parseFloat(document.getElementById('interestRate').value);
var years = parseInt(document.getElementById('loanTerm').value);
var taxRate = parseFloat(document.getElementById('propertyTax').value) / 100;
if (isNaN(annualIncome) || annualIncome <= 0) {
alert("Please enter a valid annual income.");
return;
}
var monthlyIncome = annualIncome / 12;
// Standard 28/36 Rules
var frontEndMax = monthlyIncome * 0.28;
var backEndMax = (monthlyIncome * 0.36) – monthlyDebt;
// Use the more conservative limit
var maxMonthlyPITI = Math.min(frontEndMax, backEndMax);
if (maxMonthlyPITI <= 0) {
alert("Your current debts are too high relative to your income for standard mortgage limits.");
return;
}
// PITI = P&I + (Price * TaxRate / 12)
// Monthly P&I = L * [i(1+i)^n] / [(1+i)^n – 1]
// We need to solve for Price (Home Value) where Loan (L) = Price – DownPayment
var i = (annualRate / 100) / 12;
var n = years * 12;
// Monthly P&I Factor
var factor = (i * Math.pow(1 + i, n)) / (Math.pow(1 + i, n) – 1);
// Equation: MaxMonthlyPITI = (Price – DownPayment) * factor + (Price * taxRate / 12)
// MaxMonthlyPITI = Price * factor – DownPayment * factor + Price * (taxRate / 12)
// MaxMonthlyPITI + DownPayment * factor = Price * (factor + taxRate / 12)
// Price = (MaxMonthlyPITI + DownPayment * factor) / (factor + taxRate / 12)
var maxPrice = (maxMonthlyPITI + (downPayment * factor)) / (factor + (taxRate / 12));
var maxLoan = maxPrice – downPayment;
if (maxLoan < 0) maxLoan = 0;
// Display Results
document.getElementById('affordabilityResults').style.display = 'block';
document.getElementById('maxHomePrice').innerHTML = '$' + Math.round(maxPrice).toLocaleString();
document.getElementById('maxLoanAmount').innerHTML = '$' + Math.round(maxLoan).toLocaleString();
document.getElementById('monthlyPITI').innerHTML = '$' + Math.round(maxMonthlyPITI).toLocaleString();
document.getElementById('frontEndRatio').innerHTML = '28% ($' + Math.round(frontEndMax).toLocaleString() + ')';
document.getElementById('backEndRatio').innerHTML = '36% ($' + Math.round(backEndMax + monthlyDebt).toLocaleString() + ' cap)';
// Scroll to results
document.getElementById('affordabilityResults').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}
Mortgage Affordability Calculator
Find out how much home you can actually afford based on your income.
30 Years
20 Years
15 Years
10 Years
Your Purchasing Profile
Maximum Home Price:
$0
Maximum Loan Amount:
$0
Estimated Monthly Payment (PITI):
$0
Front-End DTI Ratio:
28%
Back-End DTI Ratio:
36%
How Home Affordability is Calculated
Lenders don't just look at your salary when deciding how much you can borrow. They use specific financial metrics called Debt-to-Income (DTI) ratios to determine your "purchasing power." This calculator uses the standard 28/36 Rule, which is the benchmark for most conventional mortgage underwriting.
The 28/36 Rule Explained
- The 28% Rule (Front-End Ratio): This guideline suggests that your total housing expenses (including principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income.
- The 36% Rule (Back-End Ratio): This guideline suggests that your total debt obligations (housing expenses plus existing debts like car loans, student loans, and credit cards) should not exceed 36% of your gross monthly income.
Factors That Impact Your Budget
While income is the primary driver, several other factors can significantly shift your maximum home price:
- Interest Rates: A 1% increase in interest rates can reduce your purchasing power by roughly 10%.
- Down Payment: The more you put down, the lower your loan-to-value ratio, which may help you avoid Private Mortgage Insurance (PMI).
- Local Property Taxes: High-tax states like New Jersey or Texas require a larger portion of your monthly payment to go toward escrow, leaving less for the actual loan.
- Credit Score: Higher scores unlock lower interest rates, directly increasing how much house you can afford for the same monthly payment.
Real-World Example
If you earn $100,000 per year ($8,333/month) and have $500 in monthly car payments:
1. The 28% rule allows a housing payment of $2,333.
2. The 36% rule allows $3,000 total debt minus $500 existing debt = $2,500.
3. The lender uses the lower of the two ($2,333) as your maximum monthly housing budget.