.calculator-container {
font-family: sans-serif;
max-width: 600px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.input-group input {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
}
button:hover {
background-color: #0056b3;
}
#result {
margin-top: 20px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
#result span {
font-weight: bold;
color: #28a745;
}
var calculateMortgageAffordability = function() {
var annualIncome = parseFloat(document.getElementById("annualIncome").value);
var monthlyDebt = parseFloat(document.getElementById("monthlyDebt").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value);
var loanTerm = parseFloat(document.getElementById("loanTerm").value);
var propertyTaxes = parseFloat(document.getElementById("propertyTaxes").value);
var homeInsurance = parseFloat(document.getElementById("homeInsurance").value);
var pmi = parseFloat(document.getElementById("pmi").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(annualIncome) || isNaN(monthlyDebt) || isNaN(downPayment) || isNaN(interestRate) || isNaN(loanTerm) || isNaN(propertyTaxes) || isNaN(homeInsurance) || isNaN(pmi)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
// Lender typically allows PITI (Principal, Interest, Taxes, Insurance) + PMI to be 28-36% of gross monthly income
// We'll use a common guideline of 30% for affordability estimation.
var maxPitiPmiRatio = 0.30;
var monthlyIncome = annualIncome / 12;
var maxAllowedHousingPayment = monthlyIncome * maxPitiPmiRatio;
var maxAllowedOtherDebt = monthlyIncome – monthlyDebt; // This is a rough check; lenders look at Debt-to-Income (DTI) ratio.
// A common DTI limit is 43-50% of gross monthly income.
// For simplicity, we'll focus on the housing payment portion.
var monthlyPropertyTaxes = propertyTaxes / 12;
var monthlyHomeInsurance = homeInsurance / 12;
var monthlyPmi = pmi / 12;
// Estimate the maximum affordable loan amount
// This is a bit iterative. We need to find a loan amount (L) such that
// P + I + T + I + PMI <= maxAllowedHousingPayment
// P = Principal, I = Interest, T = Taxes, I = Insurance, PMI = Private Mortgage Insurance
// M = P [ i(1 + i)^n ] / [ (1 + i)^n – 1] where M is monthly payment, P is principal, i is monthly interest rate, n is number of months
// i = (annualInterestRate / 100) / 12
// n = loanTerm * 12
// We need to work backwards from the maximum total monthly housing cost (PITI+PMI)
// var MaxTotalMonthlyHousingCost = maxAllowedHousingPayment
// MaxTotalMonthlyHousingCost = MonthlyPrincipalAndInterest + MonthlyPropertyTaxes + MonthlyHomeInsurance + MonthlyPmi
// MonthlyPrincipalAndInterest = MaxTotalMonthlyHousingCost – MonthlyPropertyTaxes – MonthlyHomeInsurance – MonthlyPmi
var monthlyPrincipalAndInterest = maxAllowedHousingPayment – monthlyPropertyTaxes – monthlyHomeInsurance – monthlyPmi;
if (monthlyPrincipalAndInterest <= 0) {
resultDiv.innerHTML = "Based on your income and existing debts, the estimated maximum affordable housing payment may not cover taxes, insurance, and PMI. You may not be able to qualify for a mortgage with these parameters.";
return;
}
var monthlyInterestRate = (interestRate / 100) / 12;
var numberOfMonths = loanTerm * 12;
// Calculate maximum loan amount (P) using the mortgage payment formula rearranged
// P = M * [ (1 + i)^n – 1] / [ i(1 + i)^n ]
var maxLoanAmount;
if (monthlyInterestRate === 0) { // Handle zero interest rate case
maxLoanAmount = monthlyPrincipalAndInterest * numberOfMonths;
} else {
var numerator = Math.pow(1 + monthlyInterestRate, numberOfMonths) – 1;
var denominator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, numberOfMonths);
maxLoanAmount = monthlyPrincipalAndInterest * (numerator / denominator);
}
// The maximum purchase price is the maximum loan amount plus the down payment.
var maxPurchasePrice = maxLoanAmount + downPayment;
// Format results
var formattedMaxLoanAmount = maxLoanAmount.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMaxPurchasePrice = maxPurchasePrice.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
var formattedMonthlyPrincipalAndInterest = monthlyPrincipalAndInterest.toLocaleString(undefined, { style: 'currency', currency: 'USD' });
resultDiv.innerHTML = "Estimated maximum affordable loan amount: " + formattedMaxLoanAmount + "" +
"Estimated maximum affordable purchase price: " + formattedMaxPurchasePrice + "" +
"This is based on the assumption that your total monthly housing costs (Principal, Interest, Taxes, Insurance, PMI) should not exceed 30% of your gross monthly income, and your estimated monthly principal and interest payment would be approximately " + formattedMonthlyPrincipalAndInterest + ".";
};
Understanding Mortgage Affordability
Determining how much house you can afford is a crucial step in the home-buying process. A mortgage affordability calculator helps you estimate the maximum loan amount and purchase price you might qualify for, based on your financial situation and current market conditions. It's important to remember that this is an estimate, and your actual loan approval will depend on a lender's detailed underwriting process, including your credit score, debt-to-income ratio, employment history, and other factors.
Key Factors in Mortgage Affordability:
Annual Household Income: This is the primary driver of affordability. Lenders look at your gross income (before taxes) to determine how much you can borrow.
Monthly Debt Payments: Existing financial obligations such as car loans, student loans, and credit card payments significantly impact your debt-to-income (DTI) ratio. A lower DTI generally means you can afford a larger mortgage.
Down Payment: The larger your down payment, the less you need to borrow, which can lower your monthly payments and potentially help you avoid private mortgage insurance (PMI).
Interest Rate: Even small changes in the interest rate can have a substantial effect on your monthly payment and the total amount of interest you pay over the life of the loan.
Loan Term: Shorter loan terms (e.g., 15 years) have higher monthly payments but result in less interest paid overall. Longer terms (e.g., 30 years) have lower monthly payments but more interest paid over time.
Property Taxes: These are recurring taxes assessed by local governments, typically paid monthly as part of your mortgage escrow.
Homeowner's Insurance: This is required by lenders to protect against damage to the property. It's usually paid monthly via escrow.
Private Mortgage Insurance (PMI): If your down payment is less than 20% of the home's purchase price, lenders usually require PMI to protect themselves. This adds to your monthly housing cost.
How the Calculator Works:
This calculator uses common lending guidelines to estimate your affordability. It typically assumes that your total monthly housing payment—including principal, interest, property taxes, homeowner's insurance, and PMI (PITI+PMI)—should not exceed a certain percentage (often around 30%) of your gross monthly income. It then works backward to calculate the maximum loan amount and, consequently, the maximum purchase price you might be able to afford, after accounting for your down payment.
Disclaimer: This calculator provides an estimate for informational purposes only and does not constitute financial advice or a loan commitment. Consult with a mortgage professional for personalized guidance.