Estimate your available equity and potential monthly payments.
Your HELOC Summary
Maximum Credit Line:
Total Available Equity:
Estimated Monthly Interest (Interest-Only):
Remaining Equity after Draw:
How Does a HELOC Calculator Work?
A Home Equity Line of Credit (HELOC) is a revolving line of credit secured by your home. Unlike a standard home equity loan, a HELOC allows you to borrow against your equity as needed, much like a credit card.
The calculation is based primarily on your Loan-to-Value (LTV) ratio. Most lenders allow you to borrow up to 80% or 85% of your home's total value, minus what you still owe on your primary mortgage.
Example Calculation
Imagine your home is worth $500,000 and your lender permits an 80% LTV.
Total allowable debt: $500,000 x 0.80 = $400,000.
If you owe $300,000 on your mortgage, your maximum HELOC would be: $400,000 – $300,000 = $100,000.
Interest-Only vs. Principal Payments
During the "draw period" (typically the first 10 years), many HELOCs allow for interest-only payments. This keeps monthly costs low while you access funds for home renovations or debt consolidation. However, once the "repayment period" begins, your monthly payment will increase significantly as you begin paying back the principal balance.
Factors That Influence Your HELOC
Credit Score: Higher scores often unlock lower interest rates and higher LTV limits.
Debt-to-Income (DTI) Ratio: Lenders evaluate your monthly income against existing debts to ensure you can afford the credit line.
Appraised Value: Professional appraisals determine the final "Home Value" used in the math.
function calculateHELOC() {
var homeValue = parseFloat(document.getElementById('homeValue').value);
var mortgageBalance = parseFloat(document.getElementById('mortgageBalance').value);
var ltvLimit = parseFloat(document.getElementById('ltvLimit').value) / 100;
var interestRate = parseFloat(document.getElementById('interestRate').value) / 100;
var drawAmount = parseFloat(document.getElementById('drawAmount').value);
// Validation
if (isNaN(homeValue) || isNaN(mortgageBalance) || isNaN(ltvLimit)) {
alert("Please enter valid numerical values for home value, mortgage, and LTV.");
return;
}
// Logic
var totalAllowableDebt = homeValue * ltvLimit;
var maxCreditLine = totalAllowableDebt – mortgageBalance;
if (maxCreditLine < 0) {
maxCreditLine = 0;
}
var monthlyInterest = 0;
if (!isNaN(drawAmount) && !isNaN(interestRate)) {
monthlyInterest = (drawAmount * interestRate) / 12;
}
var remainingEquity = maxCreditLine – (isNaN(drawAmount) ? 0 : drawAmount);
// Formatting
var formatter = new Intl.NumberFormat('en-US', {
style: 'currency',
currency: 'USD',
});
// Display
document.getElementById('maxCredit').innerText = formatter.format(maxCreditLine);
document.getElementById('availEquity').innerText = formatter.format(totalAllowableDebt – mortgageBalance);
document.getElementById('monthlyPayment').innerText = formatter.format(monthlyInterest);
document.getElementById('remainingEquity').innerText = formatter.format(remainingEquity < 0 ? 0 : remainingEquity);
document.getElementById('helocResult').style.display = 'block';
}