The Basic Formula for Your HELOC Payment

Your home equity line of credit (HELOC) monthly payment depends on how much you've borrowed and which phase of the line you're in. During the draw period (usually 5 to 10 years), you can borrow and repay as you go, and your payment covers only the interest on what you've actually drawn. During the repayment period (usually 10 to 20 years after the draw period ends), you pay both principal and interest on the full amount you borrowed, and the payment is fixed.

The simplest calculation is for the draw period: multiply the amount you've drawn by your interest rate, then divide by 12. If you've drawn $50,000 at 8% annual interest, your monthly interest payment is ($50,000 × 0.08) ÷ 12 = $333. Some lenders let you pay interest-only during the draw period; others require you to pay down principal as well. Check your loan documents to see which applies to you.

During repayment, the math is more complex because you're paying both principal and interest on a fixed schedule. Most lenders provide an amortization schedule that shows your exact payment, but you can estimate it using the standard loan payment formula or an online calculator.

Key Takeaways

  • During the draw period, your payment is usually interest-only on the amount you've borrowed, calculated as (balance × annual rate) ÷ 12.
  • During repayment, your payment includes both principal and interest and is typically fixed for the remaining loan term.
  • Your interest rate may be variable, meaning your payment can change when the rate adjusts—check your disclosure documents to see when and how often this happens.
  • Lenders must provide an amortization schedule showing your exact payment for the repayment period, so you don't have to calculate it yourself.
  • Missing a payment or falling behind can trigger the end of your draw period early and force you into repayment immediately.

Interest-Only Payments During the Draw Period

Most HELOCs allow interest-only payments while you're drawing money. This keeps your monthly cost low because you're only paying the interest that accrues on what you've borrowed, not reducing the principal. The calculation is straightforward: take your current balance, multiply by your annual interest rate, and divide by 12.

If your HELOC has a variable rate (which most do), your payment will change when the rate changes. Your lender will notify you of rate changes and provide a new payment amount. Some HELOCs have a floor rate—a minimum rate you'll never go below—and a ceiling rate—a maximum you'll never exceed. Read your disclosure documents to find these limits, because they affect how high your payment can go.

Interest-only payments are optional on some HELOCs and required on others. If you have the choice, paying more than the interest-only amount will reduce your principal and lower your payment when you move into repayment. Many borrowers pay interest-only for a few years, then start paying down principal before the draw period ends.

Principal and Interest Payments During Repayment

When your draw period ends, your HELOC moves into repayment. You can no longer borrow new money, and your payment now includes both principal and interest. The payment is usually fixed for the entire repayment period, even if your interest rate was variable during the draw period. Some lenders convert to a fixed rate at this point; others keep the variable rate but fix the payment amount by adjusting the term.

Your lender will provide an amortization schedule showing your exact monthly payment before repayment begins. This schedule shows how much of each payment goes to principal and how much to interest. Early in repayment, most of your payment goes to interest; as time passes, more goes to principal.

If you want to estimate the payment yourself, use the standard loan payment formula: M = P × [r(1 + r)^n] / [(1 + r)^n − 1], where M is the monthly payment, P is the principal balance, r is the monthly interest rate (annual rate ÷ 12), and n is the number of months remaining. Most people use an online calculator instead of doing this by hand.

How Variable Interest Rates Affect Your Payment

Nearly all HELOCs have variable interest rates tied to a market index, usually the prime rate. When the index changes, your rate changes, and so does your payment. Your disclosure documents will tell you how often your rate adjusts (usually every month, quarter, or year) and what index it's tied to.

During the draw period, a rate increase raises your interest-only payment immediately. During repayment, a rate increase raises your fixed payment at the next adjustment date. A rate decrease lowers your payment. This is why your HELOC payment can change even though you're not borrowing more money.

To estimate how a rate change affects your payment, recalculate using the new rate. If your rate goes up 1%, your monthly payment will increase by roughly 1% of your outstanding balance divided by 12. On a $100,000 balance, a 1% rate increase costs about $83 per month. Check your loan documents for the exact adjustment dates and any caps on how much your rate can change at each adjustment.

What Happens If You Only Pay Interest

If you pay only interest during the entire draw period and make no principal payments, your balance stays the same. When repayment begins, you'll owe the full amount you borrowed, and your payment will jump significantly because now you're paying principal too. This is called payment shock, and it catches many borrowers off guard.

For example, if you borrowed $100,000 at 8% and paid interest-only for 10 years, you still owe $100,000. When you move into a 10-year repayment period at the same rate, your payment jumps from $667 per month (interest-only) to $1,213 per month (principal and interest). Your lender must disclose this possibility in your initial paperwork, but it's easy to miss.

To avoid payment shock, start paying down principal before the draw period ends, or plan to refinance into a new HELOC or loan when repayment begins. Some borrowers convert their HELOC to a home equity loan (a fixed-rate, fixed-payment loan) instead of moving into repayment.

Using Online Calculators and Amortization Tools

Most lenders provide online calculators on their websites where you can enter your balance, rate, and term to see your estimated payment. These are free and take less than a minute. Search "[your lender name] HELOC payment calculator" to find theirs.

Bankrate, NerdWallet, and other financial websites also offer HELOC calculators that work with any lender's numbers. These let you model different scenarios—what if you borrow more, what if rates go up, what if you extend the repayment period—without committing to anything.

Your lender is also required to provide an amortization schedule before you enter repayment. This shows your exact payment for every month of the repayment period. Request this in writing if your lender doesn't send it automatically, because it's the most accurate number you'll get.

When Your Payment Changes Without Your Borrowing Changing

Your HELOC payment can change for three reasons: you borrowed more money, your interest rate changed, or you moved from the draw period into repayment. The first two are obvious. The third often surprises people because they didn't borrow anything new—they just reached the date their draw period ended.

If you're on a variable rate, your payment can also change when your lender adjusts the rate. This happens on a schedule set in your disclosure documents, usually monthly, quarterly, or annually. During the draw period, a rate increase raises your interest-only payment right away. During repayment, a rate increase raises your fixed payment at the next adjustment date.

Some HELOCs have a rate cap that limits how much your rate can increase over the life of the loan. For example, your rate might never go more than 6 percentage points above your starting rate. This caps how high your payment can go, but it's not a may provide—rates can still rise significantly within that cap.

Frequently Asked Questions

What's the difference between interest-only and principal-and-interest payments?

Interest-only payments cover only the cost of borrowing; they don't reduce what you owe. Principal-and-interest payments reduce your balance and build equity. Interest-only is cheaper month-to-month but leaves you owing the full amount when the draw period ends.

Can I change my payment amount after I start repayment?

No, your payment is fixed during repayment. You can pay more than the required amount to pay off the loan faster, but you can't lower the required payment. If you can't afford it, contact your lender about refinancing into a longer-term loan.

What happens if I miss a HELOC payment?

Missing a payment can trigger the end of your draw period early, forcing you into repayment immediately. Your lender will also charge a late fee and may report the miss to credit bureaus. Contact your lender as soon as you know you'll be late to discuss options.

How do I know what my interest rate will be after it adjusts?

You don't know in advance—your rate is tied to a market index that changes daily. Your disclosure documents tell you which index and when adjustments happen. You can look up the current index value to estimate your new rate, but the exact rate depends on when your lender calculates it.

Can I convert my HELOC to a fixed-rate loan?

Some lenders offer this option, usually when your draw period ends or if rates rise significantly. Ask your lender whether conversion is available and what the terms would be. This locks in your rate and payment for the rest of the loan, eliminating rate-change risk.