Home Buying Power Calculator
.buying-power-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e1e1e1;
border-radius: 12px;
background-color: #ffffff;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.buying-power-container h2 {
color: #1a202c;
margin-top: 0;
border-bottom: 2px solid #3182ce;
padding-bottom: 10px;
}
.input-grid {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 20px;
margin-bottom: 25px;
}
.input-group {
display: flex;
flex-direction: column;
}
.input-group label {
font-weight: 600;
margin-bottom: 8px;
color: #4a5568;
font-size: 14px;
}
.input-group input {
padding: 12px;
border: 1px solid #cbd5e0;
border-radius: 6px;
font-size: 16px;
}
.btn-calculate {
background-color: #3182ce;
color: white;
padding: 15px 25px;
border: none;
border-radius: 6px;
cursor: pointer;
font-size: 18px;
font-weight: bold;
width: 100%;
transition: background-color 0.2s;
}
.btn-calculate:hover {
background-color: #2b6cb0;
}
.results-box {
margin-top: 25px;
padding: 20px;
background-color: #f7fafc;
border-radius: 8px;
border: 1px solid #edf2f7;
display: none;
}
.result-item {
margin-bottom: 15px;
}
.result-label {
font-size: 14px;
color: #718096;
display: block;
}
.result-value {
font-size: 28px;
font-weight: 800;
color: #2d3748;
}
.result-sub-value {
font-size: 18px;
font-weight: 600;
color: #4a5568;
}
.calc-article {
margin-top: 40px;
line-height: 1.6;
color: #2d3748;
}
.calc-article h3 {
color: #2c5282;
margin-top: 25px;
}
@media (max-width: 600px) {
.input-grid {
grid-template-columns: 1fr;
}
}
function calculateBuyingPower() {
var yearlyIncome = parseFloat(document.getElementById('yearlyEarnings').value);
var monthlyDebt = parseFloat(document.getElementById('monthlyLiabilities').value);
var cashContribution = parseFloat(document.getElementById('liquidCapital').value);
var ratePercent = parseFloat(document.getElementById('annualMarketRate').value);
var taxRate = parseFloat(document.getElementById('localTaxEstimate').value);
var years = parseFloat(document.getElementById('amortizationTerm').value);
if (isNaN(yearlyIncome) || isNaN(monthlyDebt) || isNaN(cashContribution) || isNaN(ratePercent) || isNaN(taxRate)) {
alert("Please fill in all fields with valid numbers.");
return;
}
// 1. Calculate Monthly Gross Income
var monthlyGross = yearlyIncome / 12;
// 2. Maximum Monthly Payment (using 36% Debt-to-Income ratio)
// This includes Principal, Interest, Taxes, and Insurance (PITI)
var dtiLimit = 0.36;
var maxTotalMonthlyPayment = (monthlyGross * dtiLimit) – monthlyDebt;
if (maxTotalMonthlyPayment <= 0) {
document.getElementById('maxPrice').innerHTML = "Insufficient Income";
document.getElementById('monthlyPITI').innerHTML = "$0";
document.getElementById('loanAmount').innerHTML = "$0";
document.getElementById('results').style.display = 'block';
return;
}
// 3. Estimate Principal & Interest portion
// Taxes and Insurance usually take up roughly 1.5% of the home value annually
// We need to solve for Price: (Price * TaxRate / 12) + PI_Payment = maxTotalMonthlyPayment
// PI_Payment = Loan * [ r(1+r)^n / ((1+r)^n – 1) ]
// Loan = Price – CashContribution
var r = (ratePercent / 100) / 12;
var n = years * 12;
var t = (taxRate / 100) / 12;
// Simplified factor for PI payment per dollar of loan
var pmtFactor = (r * Math.pow(1 + r, n)) / (Math.pow(1 + r, n) – 1);
// Algebra: (Price – Cash) * pmtFactor + (Price * t) = maxTotalMonthlyPayment
// Price * pmtFactor – Cash * pmtFactor + Price * t = maxTotalMonthlyPayment
// Price * (pmtFactor + t) = maxTotalMonthlyPayment + (Cash * pmtFactor)
// Price = (maxTotalMonthlyPayment + Cash * pmtFactor) / (pmtFactor + t)
var estimatedPrice = (maxTotalMonthlyPayment + (cashContribution * pmtFactor)) / (pmtFactor + t);
var estimatedLoan = estimatedPrice – cashContribution;
if (estimatedLoan < 0) {
estimatedLoan = 0;
estimatedPrice = cashContribution;
}
// Display results
document.getElementById('results').style.display = 'block';
document.getElementById('maxPrice').innerHTML = "$" + estimatedPrice.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
document.getElementById('monthlyPITI').innerHTML = "$" + maxTotalMonthlyPayment.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('loanAmount').innerHTML = "$" + estimatedLoan.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0});
}