Home Equity Line of Credit (HELOC) Calculator

What is a HELOC?

A Home Equity Line of Credit — HELOC — is a revolving credit facility secured by the equity you've built up in your home. Instead of receiving a single lump sum, you're approved for a maximum credit line and then draw against it as you need funds, much like a credit card that happens to be tied to your house. You pay interest only on the amount actually drawn, not on the full credit limit.

Lenders typically allow you to borrow up to 80–85% of your home's appraised value minus your existing mortgage balance. Because the loan is secured by real property, the interest rate is usually well below what you'd pay on an unsecured personal loan or a credit card. If you're shopping for the right financing vehicle, our mortgage calculator and APR calculator round out the comparison toolkit.

HELOC draw period explained

The draw period is the most flexible phase of a HELOC. During this window, you can withdraw funds in any amount up to your remaining credit limit, repay the balance whenever you have spare cash, and then re-borrow if you need to. Most US lenders set the draw period at 10 years, though shorter windows of 5–7 years exist for lower-tier products.

Because most HELOCs require only interest payments during the draw period, the monthly cost is unusually low. That's intentional — lenders want flexibility to be the headline feature — but it also means principal does not get paid down. Borrowers who treat interest-only payments as the natural plan often end the draw period owing the same balance they started with, only to face a much larger repayment-period payment.

HELOC repayment period explained

Once the draw period ends, your HELOC enters its repayment phase. The credit line is closed to new draws and the outstanding balance amortizes into a fully principal-and-interest schedule over the next 15–20 years, depending on your lender's terms. The payment jumps because you're now retiring principal in addition to paying interest.

Concrete example: a $50,000 balance at 8.5% interest costs roughly $354 a month during a 10-year interest-only draw period. The same balance amortized over a 15-year repayment period jumps to roughly $492 a month. Adding extra principal during the draw window — even $100 per month — meaningfully softens that payment shock and saves thousands in lifetime interest.

Fixed vs variable HELOC rates

Almost every HELOC sold in the US carries a variable rate tied to the prime rate plus a margin negotiated at origination. If prime is 8.5% and your margin is 0.5%, your effective HELOC rate is 9.0%. When the Federal Reserve raises the federal funds rate, prime moves with it — and so does your HELOC payment.

Some lenders offer a fixed-rate conversion option that lets you lock part of your outstanding balance at a fixed rate, behaving like a mini home-equity loan inside the line. Others advertise introductory promotional APRs — often near 0% to 4% — for the first 6–12 months. Both features are valuable, but read the fine print carefully: promo rates expire, conversion fees may apply, and locked portions often have shorter amortization windows.

Risks of HELOC borrowing

A HELOC is one of the cheapest ways to borrow against home equity, but it carries genuine risk. First, the loan is secured by your house — miss enough payments and the lender can foreclose. Second, variable rates mean the payment you can comfortably afford today might not be affordable two years from now if benchmark rates rise.

Third, the end-of-draw payment shock catches many borrowers off guard. Interest-only payments make the line feel like cheap money during the draw period, but the full balance still has to be repaid in the years that follow. Fourth, lenders can — and during the 2008 financial crisis, did — freeze undrawn portions of HELOCs if home values fall, leaving you without the emergency credit you were counting on.

How HELOC interest is calculated

HELOC interest is calculated daily on the outstanding balance. Each day, the lender multiplies your balance by the daily periodic rate (annual rate divided by 365) and adds the result to an accrued interest tally. At the end of each billing cycle, that month's accrued interest becomes your minimum payment if you're in an interest-only draw period.

Best uses for a HELOC

• Home renovations with uncertain budget. Draw only what you need as the project unfolds — pay interest only on the drawn portion, avoiding the wasted interest of a too-large lump-sum loan.
• Debt consolidation at a lower rate. Replacing credit cards charging 20%+ with a HELOC at single-digit rates can save thousands. Pair with our debt consolidation calculator to model the savings.
• Emergency liquidity backup. Opening a HELOC while your home value is high gives you a safety net you can use only if needed. Many borrowers never draw from theirs.
• Education or large medical expenses. Tuition paid each semester or unexpected medical bills can be drawn against the HELOC as costs arise rather than borrowed in one lump sum.

How a HELOC affects your credit score

Opening a HELOC produces a small, temporary drop in your FICO score from the hard inquiry and the new credit account. Over the long run, however, a responsibly managed HELOC can improve your credit profile by adding a large installment-style credit line that improves your overall credit mix and utilization ratio.

The most important credit consequence to manage is on-time payments. Because HELOCs are secured loans, missed payments are reported aggressively and can escalate to foreclosure proceedings. Set up automatic payments so a single missed bill never becomes a permanent stain on your credit report.

HELOC vs cash-out refinance

A cash-out refinance replaces your existing first mortgage with a new, larger mortgage and gives you the difference in cash. A HELOC, by contrast, sits as a second lien behind your existing mortgage and gives you a revolving line of credit. Cash-out refis usually carry lower rates because they're first-lien, but they reset the amortization clock and incur full origination fees.

HELOCs make sense when your existing first-mortgage rate is much lower than today's market rate and you don't want to lose that low rate. They also make sense for ongoing borrowing needs where a lump sum would force you to pay interest on money you might never use. Cash-out refis win when you need a large lump sum and current first-mortgage rates are near or below your existing rate.