Enter the amount you plan to borrow from the line of credit.
Results Summary
Maximum HELOC Credit Limit:$0.00
Monthly Interest-Only Payment (Draw Period):$0.00
Estimated P+I Payment (20-Year Repayment):$0.00
function calculateHELOC() {
var homeValue = parseFloat(document.getElementById('homeValue').value);
var mortgageBalance = parseFloat(document.getElementById('mortgageBalance').value);
var ltvLimit = parseFloat(document.getElementById('ltvLimit').value) / 100;
var interestRate = parseFloat(document.getElementById('interestRate').value) / 100;
var drawAmount = parseFloat(document.getElementById('drawAmount').value);
if (isNaN(homeValue) || isNaN(mortgageBalance) || isNaN(ltvLimit) || isNaN(interestRate) || isNaN(drawAmount)) {
alert("Please enter valid numbers in all fields.");
return;
}
// Calculate Max Limit
var maxLimit = (homeValue * ltvLimit) – mortgageBalance;
if (maxLimit < 0) maxLimit = 0;
// Interest Only Payment (Draw Period)
var monthlyInterestOnly = (drawAmount * interestRate) / 12;
// Fully Amortized Payment (Assuming 20 year / 240 months repayment period)
var monthlyRate = interestRate / 12;
var numMonths = 240;
var pAndI = drawAmount * (monthlyRate * Math.pow(1 + monthlyRate, numMonths)) / (Math.pow(1 + monthlyRate, numMonths) – 1);
// Update UI
document.getElementById('maxLimitText').innerText = '$' + maxLimit.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('interestOnlyText').innerText = '$' + monthlyInterestOnly.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('repaymentText').innerText = '$' + pAndI.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
document.getElementById('heloc-results').style.display = 'block';
}
How to Use the HELOC Payment Calculator
A Home Equity Line of Credit (HELOC) is a flexible revolving credit line that uses your home as collateral. Unlike a standard home equity loan, a HELOC allows you to borrow against your equity, pay it back, and borrow again during the "draw period."
Understanding the Math
Lenders typically allow you to borrow up to 80% or 85% of your home's total value, minus what you still owe on your first mortgage. This is known as the Loan-to-Value (LTV) limit.
The Limit Formula: (Home Value × LTV %) – Current Mortgage = Available Equity.
Interest-Only Phase: During the draw period (usually 10 years), most lenders only require you to pay interest on the amount you have actually spent.
Repayment Phase: After the draw period ends, you must pay back both the principal and the interest over a set term (often 20 years).
Example Calculation
Imagine your home is worth $500,000 and you owe $300,000 on your mortgage. If a lender allows an 80% LTV:
80% of $500,000 is $400,000.
Subtract your $300,000 mortgage balance.
Your maximum HELOC limit is $100,000.
If you then spend $50,000 of that line at an 8.5% interest rate, your monthly interest-only payment would be approximately $354.17.
Variable vs. Fixed Rates
Most HELOCs come with variable interest rates, meaning your monthly payment can change if the Federal Reserve adjusts interest rates. Always factor in a "buffer" when calculating your budget to ensure you can afford higher payments if rates rise.