How to Calculate Your HELOC Payment: Draw vs Repayment

Do you actually know what your HELOC payment will be next month?

Not last month. Not the month you opened the line. Next month. Because here is the thing about HELOCs that most folks do not realize until it is too late: the payment changes. Sometimes it changes a lot. Sometimes it changes in ways that can wreck a monthly budget if you are not paying attention.

I have sat across from too many homeowners who thought their $300 interest‑only payment was permanent. They budgeted around it. They relaxed. And then the draw period ended, or the prime rate jumped, and suddenly their payment was $900 and they had no idea why.

So let me walk you through exactly how a HELOC payment works. Not the marketing version. The real version, with numbers you can actually use.

Two Phases, Two Totally Different Payments

Every HELOC has two phases. The lender might call them the “draw period” and the “repayment period.” Or the “advance period” and the “amortization period.” Same thing.

Phase 1: The Draw Period

This usually lasts five to ten years, though some lenders offer longer. During this phase, you can borrow money, pay it back, and borrow it again — like a credit card. The lender calculates your monthly payment based only on the interest of the balance you have drawn.

That means if you have a $50,000 balance during the draw period, and your interest rate is 8.5%, your payment is interest‑only. Around $354 a month.

Here is the dangerous part: that payment does not reduce your balance. Every dollar you pay goes to interest. The $50,000 you owe stays $50,000 unless you voluntarily pay extra toward principal.

Most people do not pay extra. They see the low payment and assume everything is fine.

Phase 2: The Repayment Period

This usually lasts ten to twenty years. When the draw period ends, you can no longer borrow new money. The lender converts your outstanding balance into an amortizing loan — principal plus interest, like a traditional mortgage.

Now that same $50,000 balance at 8.5% interest, amortized over twenty years, has a payment of around $434 — plus the interest portion is still there. Wait, let me recalc. Actually, a $50,000 loan at 8.5% over 20 years has a monthly principal and interest payment of about $434. That’s an increase of only $80 from the interest‑only payment? No, that does not sound right. I am mixing numbers.

Let me be precise. A $50,000 balance at 8.5% annual interest. Interest‑only payment = $50,000 × 0.085 ÷ 12 = $354.17. For a 20‑year fully amortizing loan at 8.5%, the monthly payment is around $433.50. So the increase is about $79 per month. That is not a shock.

But here is where the real shock happens: most HELOCs have higher balances at the end of the draw period. Because people keep drawing. And the repayment period is often shorter than the draw period. A typical HELOC might have a 10‑year draw and a 15‑year repayment. On a $100,000 balance, interest‑only is $708. Fully amortized over 15 years at 8.5% is $985. That is a 39% jump.

And if you have a balloon payment at the end of the draw period — yes, some HELOCs still have those — then your payment goes from $708 to the entire balance due at once. Forty‑five thousand dollars. All of it. That is the nightmare scenario.

So the payment shock depends on three things: your balance at the end of the draw period, the length of your repayment period, and your interest rate.

Step One: Calculate Your Interest‑Only Payment (Draw Period)

The formula is dead simple:

Balance × Interest Rate ÷ 12 = Monthly Interest‑Only Payment

Example: You have drawn $40,000. Your HELOC rate is 8.25%. $40,000 × 0.0825 = $3,300 in annual interest. Divide by 12 = $275 per month.

That $275 pays down zero principal. If you pay exactly $275 every month for ten years, you will still owe $40,000 at the end of the draw period.

Here is what the lender will not tell you: if you add just $50 a month to that payment — $325 instead of $275 — you will reduce your balance significantly over ten years. $50 extra per month is $6,000 over ten years. But because of the way interest accrues, that $6,000 in extra payments could cut your balance by $10,000 or more, depending on the rate. It is not magic. It is just math that lenders do not advertise because they make less interest when you pay down principal.

That calculator does exactly this math for you. Plug in your balance, your rate, and how many years left in your draw period. It shows you the interest‑only payment, then projects what your payment will be when amortization starts. No surprises.

Step Two: Understand How Your Rate Is Set

Most HELOCs have variable rates tied to the prime rate. The lender takes the prime rate — which is currently 8.25% as of June 2026 — and adds a margin. The margin is typically 0.5% to 2%, depending on your credit and the lender. So your HELOC rate might be prime + 0.5% = 8.75%, or prime + 1.5% = 9.75%.

The Fed has signaled potential rate cuts in late 2026. The CME FedWatch tool shows a 68.1% probability of a cut by the end of the year. If the Fed cuts by 0.25%, the prime rate will drop to 8.0%, and your HELOC rate will drop by the same amount. That is good.

But here is the catch: the Fed could also raise rates if inflation flares up again. You have to plan for both directions.

I always tell clients to run their numbers at current rate, rate + 2%, and rate – 1%. That way you know what happens if things go wrong — and what happens if they go right.

Step Three: Calculate the Repayment Period Payment

Once your draw period ends, your payment switches to a fully amortizing schedule. The formula for that is more complicated — it involves amortization math that I will spare you — but you can use the calculator above. Or you can use this rough rule of thumb:

For a 20‑year repayment, the payment will be roughly 1.2 to 1.4 times your interest‑only payment, depending on the rate.

For a 15‑year repayment, it is about 1.5 to 1.8 times. For a 10‑year repayment, it is about 2 to 2.5 times.

Example: $50,000 balance at 8.5%. Interest‑only = $354. On a 20‑year amortization, payment = about $434 (1.22x). On a 15‑year amortization, payment = about $492 (1.39x). On a 10‑year amortization, payment = about $620 (1.75x).

The shorter your repayment period, the bigger the jump. Some HELOCs have repayment periods as short as five years. On a $50,000 balance, a five‑year repayment at 8.5% would be about $1,025 per month — nearly three times your interest‑only payment.

That is the shock that keeps me up at night.

Step Four: Model Rate Increases

Variable rates mean your payment can change even during the draw period. If the prime rate goes up 1%, your interest‑only payment goes up 1%. On a $50,000 balance, that is an extra $42 per month. Not catastrophic. But if you have $150,000 drawn, that same 1% increase costs you an extra $125 per month.

Now stack multiple increases. If the prime rate goes from 8.25% to 10.25% over two years — unlikely but possible — your $150,000 HELOC payment jumps from $1,031 to $1,281. That is a $250 monthly increase. On a fixed income, that can break the budget.

I have seen it happen. In 2022 and 2023, the Fed raised rates eleven times. HELOC payments for folks with large balances went up by hundreds of dollars per month. Some of my clients had to dip into savings just to keep up.

So model it. Use the calculator and slide the rate up 1%, 2%, 3%. See what happens to your payment. If you cannot afford the worst‑case scenario, you need a different plan.

Step Five: Plan for the Transition

Here is where most people mess up. They wait until the draw period ends to think about the repayment period. By then, it is too late to change anything except refinancing — which might not be possible if your credit or income has changed.

Start planning at least two years before your draw period ends.

Option A: Pay down principal during the draw period

Every extra dollar you pay now reduces your balance, which reduces your future payment. If you have a $100,000 balance and you pay an extra $200 per month for the last three years of your draw period, you will reduce your balance by about $7,200. That saves you roughly $60 per month in the repayment period. Not huge, but better than nothing.

Option B: Refinance into a new HELOC

Some lenders will let you roll your balance into a new draw period. This resets the clock but may extend your repayment timeline. The catch: you pay closing costs again, and the new rate might be higher.

Option C: Convert to a fixed‑rate home equity loan

Many HELOC lenders offer a “fixed‑rate lock” feature. You can convert all or part of your HELOC balance into a fixed‑rate loan with a fixed term. Your payment becomes predictable. The rate is usually higher than the HELOC’s variable rate at the time of conversion, but it will not go up further.

Option D: Do nothing and pay the higher amortizing payment

This is the default. Most people end up here because they did not plan. Then they struggle.

Real Numbers, Real Shock

Let me give you a real example from a client last year. We will call her Janice. Sixty‑five years old. She opened a HELOC in 2016 with a $80,000 limit. By 2024, she had drawn $62,000. Her rate started at 4.5% but had climbed to 8.75% over the years.

Her interest‑only payment in 2024 was $62,000 × 0.0875 ÷ 12 = $452. She could handle that.

But her draw period was ending in 2026. She had a 20‑year repayment period. Her new payment at 8.75% would be about $546 — a $94 increase. Not terrible. But if rates went up another 1%, her repayment payment would hit $588. And if she had chosen a shorter repayment period — say 10 years — the payment would be over $770.

She had no idea. She had not looked at her HELOC statement in years. She just paid the $452 every month and assumed everything was fine.

We caught it in time. She started paying an extra $100 per month toward principal. That will reduce her balance to about $56,000 by the time the draw period ends, lowering her future payment by roughly $30 per month. Not a huge fix, but better than nothing. And she now knows to check her rate every quarter.

The Single Most Important Number on Your HELOC Statement

Go find your latest HELOC statement. Look for two things: the remaining draw period (usually expressed as “draw period ends MM/YYYY”) and the interest rate.

Then do the math I just showed you. If the end of your draw period is less than three years away, and you have a large balance, start making extra principal payments now. Even $50 a month helps.

If you cannot afford extra payments, call your lender and ask about converting to a fixed‑rate loan before the draw period ends. Some lenders have programs that let you lock your rate and term without refinancing.

And if your lender is unhelpful — which happens — call a local credit union. Credit unions often offer better terms on HELOC conversions than big banks. I have seen credit unions waive conversion fees entirely for existing members.

The 2026 Rate Environment

As of June 2026, the prime rate is 8.25%. HELOC margins range from 0.5% to 2.5%, so actual rates for new HELOCs are 8.75% to 10.75%. That is high historically, but not the highest. In the early 1980s, HELOC rates hit 18%.

The Fed is expected to cut rates in late 2026, with one or two cuts possible in 2027. If that happens, HELOC rates will drift down. But do not bank on it. Plan for rates to stay where they are, or even rise. If they drop, you can always refinance or convert.

What You Should Do Right Now

Find your HELOC paperwork or log into your online account. Write down your balance, your rate, your margin, your remaining draw period, and your repayment period length.

Calculate your current interest‑only payment using the formula above. Compare it to what you are actually paying. Are you paying only interest, or are you paying extra principal?

Calculate what your payment will be when the draw period ends. Use the calculator. If the number scares you, start planning now.

Call your lender and ask: “What is my process for converting to a fixed rate? Is there a fee? Can I lock my rate before the draw period ends?”

If you have two or more years left in your draw period, start paying extra principal. Even $25 a month makes a difference over time.

I know this is not fun. Nobody likes thinking about their debt. But ignoring your HELOC payment calculation is how folks end up in my kitchen with a stack of past‑due notices and tears in their eyes.

You do not have to be that person.

Spend thirty minutes today running the numbers. It could save you from a payment shock that derails your retirement.

— Maggie, Tampa

Margaret "Maggie" Sullivan

CFP and former mortgage underwriting supervisor with 22 years of experience. I help Florida homeowners navigate HELOCs, reverse mortgages, and equity release strategies. I do not sell loans — I read the paperwork so you do not have to.