.calc-wrapper {
background: #f9f9f9;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
border: 1px solid #e1e1e1;
margin-bottom: 40px;
}
.calc-title {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 28px;
font-weight: 700;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #555;
}
.input-group input, .input-group select {
width: 100%;
padding: 12px;
border: 1px solid #ddd;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group input:focus {
border-color: #3498db;
outline: none;
box-shadow: 0 0 0 2px rgba(52,152,219,0.2);
}
.row {
display: flex;
gap: 20px;
flex-wrap: wrap;
}
.col {
flex: 1;
min-width: 200px;
}
.calc-btn {
width: 100%;
padding: 15px;
background-color: #27ae60;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
margin-top: 10px;
}
.calc-btn:hover {
background-color: #219150;
}
.result-box {
margin-top: 30px;
padding: 25px;
background-color: #ffffff;
border-left: 5px solid #27ae60;
border-radius: 4px;
display: none;
box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.result-title {
color: #7f8c8d;
font-size: 14px;
text-transform: uppercase;
letter-spacing: 1px;
margin-bottom: 5px;
}
.result-value {
font-size: 36px;
color: #2c3e50;
font-weight: 800;
margin-bottom: 10px;
}
.result-detail {
font-size: 15px;
color: #666;
padding: 5px 0;
border-bottom: 1px solid #eee;
}
.error-msg {
color: #c0392b;
text-align: center;
margin-top: 10px;
display: none;
}
.content-section {
padding: 20px 0;
}
.content-section h2 {
color: #2c3e50;
margin-top: 30px;
}
.content-section h3 {
color: #34495e;
margin-top: 25px;
}
.content-section ul {
padding-left: 20px;
}
.content-section li {
margin-bottom: 10px;
}
function calculateAffordability() {
var incomeInput = document.getElementById("annualIncome").value;
var debtInput = document.getElementById("monthlyDebt").value;
var downPaymentInput = document.getElementById("downPayment").value;
var rateInput = document.getElementById("interestRate").value;
var termInput = document.getElementById("loanTerm").value;
var resultBox = document.getElementById("resultBox");
var errorMsg = document.getElementById("errorMsg");
// Validation
if (incomeInput === "" || rateInput === "" || termInput === "") {
errorMsg.style.display = "block";
resultBox.style.display = "none";
return;
}
var annualIncome = parseFloat(incomeInput);
var monthlyDebt = parseFloat(debtInput) || 0;
var downPayment = parseFloat(downPaymentInput) || 0;
var interestRate = parseFloat(rateInput);
var loanTermYears = parseInt(termInput);
if (isNaN(annualIncome) || isNaN(interestRate) || isNaN(loanTermYears)) {
errorMsg.style.display = "block";
resultBox.style.display = "none";
return;
}
errorMsg.style.display = "none";
// Logic: 28/36 Rule
var monthlyGrossIncome = annualIncome / 12;
// Front-end Ratio (28% of income for housing)
var frontEndLimit = monthlyGrossIncome * 0.28;
// Back-end Ratio (36% of income for housing + debts)
var backEndLimit = (monthlyGrossIncome * 0.36) – monthlyDebt;
// Determine max allowable monthly housing payment
var maxMonthlyHousingBudget = Math.min(frontEndLimit, backEndLimit);
var limitingFactorText = (frontEndLimit < backEndLimit) ? "Front-End Ratio (Income)" : "Back-End Ratio (Debt)";
if (maxMonthlyHousingBudget <= 0) {
document.getElementById("maxHomePrice").innerText = "$0";
document.getElementById("monthlyPaymentResult").innerText = "$0";
document.getElementById("limitingFactor").innerText = "Debt too high relative to income";
resultBox.style.display = "block";
return;
}
// Estimate P&I capacity
// Assume 15% of the housing budget goes to Tax & Insurance, leaving 85% for Principal & Interest
var availableForPI = maxMonthlyHousingBudget * 0.85;
// Mortgage Calculation for Loan Amount
// P = (M * (1 – (1+r)^-n)) / r
var r = (interestRate / 100) / 12;
var n = loanTermYears * 12;
var maxLoanAmount = 0;
if (r === 0) {
maxLoanAmount = availableForPI * n;
} else {
maxLoanAmount = (availableForPI * (1 – Math.pow(1 + r, -n))) / r;
}
var maxPrice = maxLoanAmount + downPayment;
// Formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
maximumFractionDigits: 0
});
document.getElementById("maxHomePrice").innerText = formatter.format(maxPrice);
document.getElementById("monthlyPaymentResult").innerText = formatter.format(maxMonthlyHousingBudget);
document.getElementById("limitingFactor").innerText = limitingFactorText;
resultBox.style.display = "block";
}
How Much House Can I Afford?
Determining "how much house can I afford" is the critical first step in the home buying process. This Mortgage Affordability Calculator helps you estimate your purchasing power by analyzing your income, existing debts, and down payment capabilities against current market interest rates.
Unlike simple mortgage calculators that just output a monthly payment, this tool uses the Debt-to-Income (DTI) ratios preferred by lenders to give you a realistic maximum home price.
Understanding the 28/36 Rule
Most financial advisors and mortgage lenders use the "28/36 rule" to determine affordability. This rule consists of two thresholds:
- The Front-End Ratio (28%): Your total monthly housing costs (principal, interest, taxes, and insurance) should not exceed 28% of your gross monthly income.
- The Back-End Ratio (36%): Your total monthly debt payments (housing costs plus credit cards, student loans, car payments, etc.) should not exceed 36% of your gross monthly income.
Our calculator computes both scenarios and uses the lower number to ensure you don't overextend your finances. If you carry significant monthly debt, your affordability will likely be capped by the back-end ratio.
Key Factors Affecting Your Purchasing Power
Several variables influence the final price of the home you can buy:
1. Down Payment
A larger down payment increases your purchasing power directly. Not only does it reduce the loan amount required, but it also demonstrates financial stability to lenders. Putting down at least 20% also eliminates the need for Private Mortgage Insurance (PMI).
2. Interest Rates
Even a small fluctuation in interest rates can significantly impact your buying power. As rates rise, the portion of your monthly payment going toward interest increases, reducing the loan amount you can support with the same income.
3. Monthly Debts
Reducing your recurring monthly debts is often the fastest way to increase your home budget. Paying off a car loan or lowering credit card balances frees up monthly cash flow that can be redirected toward a mortgage.
How to Improve Your Affordability
If the results above are lower than expected, consider these strategies:
- Pay down high-interest debt: Lowering your monthly obligations improves your back-end DTI ratio.
- Save for a larger down payment: This reduces the amount you need to borrow.
- Improve your credit score: A better score often qualifies you for lower interest rates, which boosts your purchasing power.
- Look for lower property taxes: Areas with lower taxes allow more of your monthly payment to go toward the principal of the loan.