Use this calculator to estimate how much home you can afford based on your income, debts, and down payment. It's a crucial first step in your home-buying journey.
.calculator-container {
font-family: sans-serif;
border: 1px solid #ccc;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
background-color: #f9f9f9;
}
.calculator-container h2 {
text-align: center;
margin-bottom: 15px;
color: #333;
}
.calculator-container p {
text-align: center;
color: #555;
margin-bottom: 25px;
}
.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: #444;
}
.input-group input {
padding: 10px;
border: 1px solid #ddd;
border-radius: 4px;
box-sizing: border-box; /* Include padding and border in the element's total width and height */
}
button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 16px;
cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 10px;
}
button:hover {
background-color: #0056b3;
}
.calculator-result {
margin-top: 25px;
padding: 15px;
background-color: #e9ecef;
border: 1px solid #ced4da;
border-radius: 4px;
text-align: center;
font-size: 1.1em;
color: #333;
}
.calculator-result strong {
color: #007bff;
}
function calculateAffordability() {
var grossMonthlyIncome = parseFloat(document.getElementById("grossMonthlyIncome").value);
var monthlyDebtPayments = parseFloat(document.getElementById("monthlyDebtPayments").value);
var downPayment = parseFloat(document.getElementById("downPayment").value);
var interestRate = parseFloat(document.getElementById("interestRate").value) / 100; // Convert annual rate to monthly
var loanTermYears = parseInt(document.getElementById("loanTermYears").value);
var propertyTaxesAnnual = parseFloat(document.getElementById("propertyTaxesAnnual").value);
var homeInsuranceAnnual = parseFloat(document.getElementById("homeInsuranceAnnual").value);
var pmiPercentage = parseFloat(document.getElementById("pmiPercentage").value) / 100; // Convert annual percentage to monthly
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// — Input Validation —
if (isNaN(grossMonthlyIncome) || grossMonthlyIncome <= 0) {
resultDiv.innerHTML = "Please enter a valid Gross Monthly Income.";
return;
}
if (isNaN(monthlyDebtPayments) || monthlyDebtPayments < 0) {
resultDiv.innerHTML = "Please enter a valid Total Monthly Debt Payments.";
return;
}
if (isNaN(downPayment) || downPayment < 0) {
resultDiv.innerHTML = "Please enter a valid Down Payment Amount.";
return;
}
if (isNaN(interestRate) || interestRate < 0) {
resultDiv.innerHTML = "Please enter a valid Annual Interest Rate.";
return;
}
if (isNaN(loanTermYears) || loanTermYears <= 0) {
resultDiv.innerHTML = "Please enter a valid Loan Term in Years.";
return;
}
if (isNaN(propertyTaxesAnnual) || propertyTaxesAnnual < 0) {
resultDiv.innerHTML = "Please enter a valid Estimated Annual Property Taxes.";
return;
}
if (isNaN(homeInsuranceAnnual) || homeInsuranceAnnual < 0) {
resultDiv.innerHTML = "Please enter a valid Estimated Annual Homeowner's Insurance.";
return;
}
if (isNaN(pmiPercentage) || pmiPercentage < 0) {
resultDiv.innerHTML = "Please enter a valid PMI Percentage.";
return;
}
// — Calculations —
// Lenders typically use the "front-end" (housing) and "back-end" (debt-to-income) ratios.
// Common DTI limits are 28% for front-end and 36% for back-end, though these can vary.
// We'll use a common guideline of 36% for the back-end ratio as a conservative estimate for maximum PITI.
var maxTotalHousingPayment = grossMonthlyIncome * 0.36;
var availableForMortgagePrincipalAndInterest = maxTotalHousingPayment – monthlyDebtPayments;
if (availableForMortgagePrincipalAndInterest 0) {
var pmiFactor = 1 + pmiPercentage; // PMI is often calculated on the loan amount, so we factor it in.
// This is a simplification, actual PMI calculation can be more complex.
// We'll assume PMI cost is a percentage of the loan amount per year, divided by 12.
// The total monthly payment (PITI + PMI) we can afford is availableForMortgagePrincipalAndInterest.
// Let's find the maximum Principal and Interest (P&I) payment first.
// This requires a bit of iteration or a more complex financial formula if PMI is truly variable based on loan balance.
// For simplicity, let's assume a fixed PMI based on the *initial* loan amount.
// A common approach is to estimate loan amount, calculate PMI, subtract PMI from total housing payment, then calculate P&I.
// We can iterate or use a formula. Let's try a direct formula approach first, but acknowledge it's an approximation.
// A more robust method would be to use an iterative approach or a financial calculator library.
// For this example, let's try to estimate and then refine.
// The full monthly payment will be P&I + Property Taxes + Home Insurance + PMI.
// var the maximum P&I payment be 'PI_max'.
// Then, PI_max + monthlyPropertyTaxes + monthlyHomeInsurance + (loanAmount * pmiPercentage / 12) = availableForMortgagePrincipalAndInterest
// PI_max = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance – (loanAmount * pmiPercentage / 12)
// We know PI_max = P * [ i(1 + i)^n ] / [ (1 + i)^n – 1]
// So, P * [ i(1 + i)^n ] / [ (1 + i)^n – 1] = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance – (P * pmiPercentage / 12)
// P * ( [ i(1 + i)^n ] / [ (1 + i)^n – 1] + pmiPercentage / 12 ) = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance
var monthlyPmiRate = pmiPercentage / 12;
var monthlyHousingCostsExcludingPmi = monthlyPropertyTaxes + monthlyHomeInsurance;
if (availableForMortgagePrincipalAndInterest < monthlyHousingCostsExcludingPmi) {
resultDiv.innerHTML = "Your estimated monthly housing costs (taxes + insurance) already exceed your affordable housing payment based on DTI. You may need to adjust your search criteria or income/debt.";
return;
}
var remainingForPmiAndPI = availableForMortgagePrincipalAndInterest – monthlyHousingCostsExcludingPmi;
// This is still tricky. Let's reframe: Maximum PITI+PMI is `availableForMortgagePrincipalAndInterest`.
// var `MaxPI` be the maximum Principal and Interest payment.
// `MaxPI = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance – (EstimatedLoanAmount * monthlyPmiRate)`
// This requires estimating the loan amount. We'll use an iterative approximation or a simplified formula.
// Simplified approach: Assume PMI is a fixed percentage of the target loan amount.
// `Max P&I Payment = Total Affordable Housing – Monthly Taxes – Monthly Insurance – (Loan Amount * PMI Rate)`
// `Loan Amount = Max P&I Payment * ( (1 + i)^n – 1) / ( i(1 + i)^n )`
// Substitute `Max P&I Payment` into the loan amount formula.
// `Loan Amount = (Total Affordable Housing – Monthly Taxes – Monthly Insurance – (Loan Amount * PMI Rate)) * ( (1 + i)^n – 1) / ( i(1 + i)^n )`
// This is complex. A simpler, though slightly less precise, approach for a calculator is to FIRST calculate the maximum affordable loan amount assuming NO PMI,
// THEN calculate the PMI on that loan amount, subtract it from the total affordable housing payment, and THEN recalculate the maximum loan amount.
// Or, we can use an average assumption.
// Let's try a common simplification: The maximum loan amount is based on the total budget minus taxes and insurance, and then we'll find a loan amount such that its P&I + its PMI fits.
// `Monthly P&I Payment = P * monthlyInterestRate * (1 + monthlyInterestRate)^loanTermMonths / ((1 + monthlyInterestRate)^loanTermMonths – 1)`
// `Max Affordable P&I = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance`
// Calculate the maximum loan amount based on this Max Affordable P&I.
var maxAffordablePI = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance;
if (maxAffordablePI <= 0) {
resultDiv.innerHTML = "Your estimated monthly housing costs (taxes + insurance) alone exceed your affordable housing payment based on DTI. You may need to adjust your search criteria or income/debt.";
return;
}
var denominator_pi = Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1;
if (denominator_pi === 0) { // Handle case where interest rate is 0
loanAmount = maxAffordablePI * loanTermMonths / (1 + monthlyPmiRate); // Simplified if rate is 0
} else {
loanAmount = maxAffordablePI * (Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTermMonths));
}
// Now, let's factor in PMI more directly. The loan amount calculated above is what can be financed if the *entire* budget is for P&I.
// We need a loan amount (L) such that:
// `(P&I for L) + monthlyPropertyTaxes + monthlyHomeInsurance + (L * monthlyPmiRate) 0.01 && iterations < maxIterations) {
previousLoanAmount = currentLoanAmount;
var currentMonthlyPmi = currentLoanAmount * monthlyPmiRate;
var budgetForPI = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance – currentMonthlyPmi;
if (budgetForPI 0) {
var denominator = Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1;
if (denominator === 0) { // Handle 0 interest rate edge case
currentLoanAmount = budgetForPI * loanTermMonths;
} else {
currentLoanAmount = budgetForPI * (Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1) / (monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTermMonths));
}
} else {
currentLoanAmount = budgetForPI * loanTermMonths; // If interest rate is 0, principal decreases linearly
}
iterations++;
}
loanAmount = currentLoanAmount; // Use the iteratively found loan amount
} else { // Interest rate is 0
var monthlyPmi = loanAmount * (pmiPercentage / 12);
var monthlyPI = availableForMortgagePrincipalAndInterest – monthlyPropertyTaxes – monthlyHomeInsurance – monthlyPmi;
if (monthlyPI <= 0) {
loanAmount = 0;
} else {
loanAmount = monthlyPI * loanTermMonths; // Principal only loan, paid off over term
}
}
if (loanAmount 0) {
var numerator = monthlyInterestRate * Math.pow(1 + monthlyInterestRate, loanTermMonths);
var denominator = Math.pow(1 + monthlyInterestRate, loanTermMonths) – 1;
estimatedMonthlyPI = loanAmount * (numerator / denominator);
} else {
estimatedMonthlyPI = loanAmount / loanTermMonths; // Interest-free loan
}
var totalEstimatedMonthlyPayment = estimatedMonthlyPI + monthlyPropertyTaxes + monthlyHomeInsurance + estimatedMonthlyPmi;
resultDiv.innerHTML = `
Based on your inputs:
Estimated Maximum Loan Amount: $${loanAmount.toFixed(2)}
Estimated Maximum Home Price (Loan + Down Payment): $${maxHomePrice.toFixed(2)}
Estimated Total Monthly Payment (P&I + Taxes + Insurance + PMI): $${totalEstimatedMonthlyPayment.toFixed(2)}Note: This is an estimate and does not guarantee loan approval. Actual loan amounts depend on lender policies, credit score, loan type, and other factors. Property taxes, insurance, and PMI costs can vary.
`;
}