The basic formula for a HELOC payment

A HELOC payment is calculated by multiplying your current balance by your interest rate, then dividing by 12 to get a monthly charge. If you have a $50,000 balance at 8% annual interest, you divide $50,000 by 12.5 (which is 100 divided by 8%) to get your monthly interest payment of about $333. If your HELOC requires you to pay principal as well, you add that amount to the interest.

Most HELOCs work in two phases: a draw period (usually 5 to 10 years) where you can borrow and often pay interest-only, and a repayment period (usually 10 to 20 years) where you cannot borrow anymore and must pay both principal and interest. The payment calculation changes between these phases because the repayment phase requires you to pay down the full balance.

Your lender provides a payment calculator or statement showing your exact payment, but understanding the math behind it helps you see how interest rate changes affect what you owe each month.

Key Takeaways

  • During the draw period, most HELOC payments cover interest only, calculated as your balance multiplied by your annual rate and divided by 12.
  • When you move to the repayment period, your payment jumps because you now pay both principal and interest over a fixed number of years.
  • Your payment changes every time your interest rate adjusts if you have a variable-rate HELOC, which is the most common type.
  • The payment formula assumes you make no new borrowing; if you draw more during the draw period, your payment increases.

Interest-only payments during the draw period

During the draw period, most lenders let you pay interest only. This keeps your monthly payment low, but you build no equity and owe the full balance when the draw period ends. The calculation is straightforward: take your outstanding balance, multiply by your annual interest rate, and divide by 12.

Example: You have drawn $75,000 on your HELOC at 7.5% interest. Your monthly interest-only payment is ($75,000 × 0.075) ÷ 12 = $468.75. If you make only this payment, you still owe the full $75,000 when the draw period ends. Some homeowners pay extra principal during this phase to reduce what they owe later.

If your rate is variable, this payment recalculates whenever your rate changes. A 1% rate increase on that $75,000 balance raises your monthly payment by $62.50. This is why variable-rate HELOCs can feel like a moving target—your payment is not locked in.

Principal-and-interest payments during repayment

When the draw period ends, your HELOC enters the repayment phase. Now you cannot borrow anymore, and your payment must cover both interest and principal over a set term—typically 10 to 20 years. This payment is calculated the same way a mortgage payment is: using an amortization formula that spreads the balance over the remaining years.

Your lender calculates this for you, but the payment is higher than interest-only because you are paying down the debt. If you owe $60,000 at the start of a 15-year repayment period at 7% interest, your monthly payment will be roughly $560 per month. In the early months, most of that goes to interest; by the end, most goes to principal.

The shock many homeowners face is that their payment can double or triple when they move from draw to repayment. If you were paying $300 interest-only, you might suddenly owe $600 or more. Planning for this jump is critical—some homeowners start paying principal during the draw period to soften the blow.

How rate changes affect your payment

Nearly all HELOCs have variable interest rates tied to an index like the prime rate. When the index moves, your rate moves with it (after any rate cap takes effect), and your payment recalculates. During the draw period, a rate increase raises your interest-only payment. During repayment, it raises your total payment and may extend your payoff date if your lender allows it.

Your HELOC agreement specifies how often your rate can adjust—usually every month, quarter, or year—and whether there are caps on how much it can move at once or over the life of the loan. A 2% rate increase on a $100,000 balance during repayment can add $150 to $200 to your monthly payment, depending on how many years remain.

This is why some homeowners convert part or all of their HELOC balance to a fixed-rate loan when rates are low. It locks in the payment and removes the uncertainty, though it usually means losing the ability to borrow more.

What happens if you make extra payments

Any payment above the minimum goes straight to principal, reducing your balance and the interest you pay going forward. If your minimum is $400 and you pay $500, that extra $100 cuts your balance and lowers next month's interest charge slightly.

During the draw period, paying extra principal is optional but smart if you can afford it. It reduces the shock when repayment begins. During repayment, extra payments shorten how long you owe the HELOC and save you thousands in interest over the life of the loan.

Some lenders charge a fee for early payoff or have minimum payment requirements, so check your agreement before you assume extra payments are free. Most do not charge a penalty, and many lenders welcome the early payoff.

Using your lender's payment calculator

Your HELOC statement or your lender's website usually includes a payment calculator. You enter your balance, interest rate, and remaining term, and it shows your monthly payment. This is faster and more accurate than doing the math yourself, especially for repayment-phase calculations.

If you are considering drawing more or want to see how a rate change would affect you, the calculator lets you test different scenarios. Some lenders also show an amortization schedule—a month-by-month breakdown of how much of each payment goes to interest versus principal.

If your lender does not offer a calculator online, call and ask them to run the numbers for you. They can also tell you exactly when your draw period ends and what your repayment payment will be, which is information every HELOC holder should have.

Frequently Asked Questions

Why does my HELOC payment change every month?

If your rate is variable, your payment changes whenever your interest rate adjusts. During the draw period, a rate change affects your interest-only payment. During repayment, it affects your total payment. Some lenders adjust rates monthly; others quarterly or annually. Check your agreement for the adjustment schedule.

Can I pay only interest during the repayment period?

No. Once the draw period ends, your lender requires you to pay principal as well as interest. This is written into your agreement. If you cannot afford the higher payment, you may be able to refinance the balance into a fixed-rate loan or personal loan, but you cannot stay on interest-only indefinitely.

What if I draw more money during the draw period—does my payment go up?

Yes. Each time you draw, your balance increases, and so does your interest-only payment. If you draw an additional $20,000, your monthly payment rises by roughly $167 (at 10% interest). This is why some homeowners treat a HELOC like a credit card and end up with a much larger payment than they expected.

How much will my payment jump when I move from draw to repayment?

It depends on your balance, rate, and repayment term. A rough estimate: if you owe $100,000 at 7% interest over 15 years, your payment will be around $1,000 per month instead of $583 interest-only. The exact number depends on your lender's calculation, so ask them for a projection before the draw period ends.

Is there a way to lock in my HELOC payment?

You cannot lock in a variable-rate HELOC payment, but you can convert the balance to a fixed-rate loan or refinance into a fixed-rate home equity loan. This removes the rate risk but usually means losing the ability to borrow more and may involve closing costs or a new application.