How to Calculate a HELOC Payment
Bills Bottom Line
A HELOC has two payment phases that work very differently. During the draw period, which is usually 10 years, you generally only pay interest on what you have actually borrowed. When repayment begins, your payment usually increases to cover principal, too. Knowing both numbers before you sign could save you from a significant budget surprise later.
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Imagine you took out a HELOC. You got approved for $75,000. You drew $50,000 to renovate your kitchen. For 10 years, the payment is manageable—interest only on what you borrowed. Then Year 11 arrives. The payment is not the same number anymore.
A HELOC has two phases, which may come with two completely different payment structures and most HELOCs have a variable rate that could go up or down. That is the thing to understand before you borrow.
Here is how to calculate a HELOC payment—and what your numbers could actually look like.
How HELOC payments work
To calculate a HELOC payment during the draw period, you typically multiply your outstanding balance by your annual interest rate and divide by 12. During the repayment period, payments are generally higher because they cover both principal and interest, amortized over the remaining loan term—typically 10 to 20 years.
In plain English: you borrow what you need, generally make interest-only payments during the draw period, then pay it all back—principal included—once the repayment period begins..
Draw periods typically last 10 years. Repayment periods typically run 10-20 years, but check your loan agreement for your specific terms. Some HELOCs may require a balloon payment—a large lump sum at the end of the draw period—if you have made only minimum payments. That's not universal but worth confirming before you sign.
Because a HELOC is secured by your home, the lender could eventually foreclose if payments are not made. That is the trade-off for a lower rate—and HELOCs typically carry lower rates than personal loans or credit cards.
How to calculate your draw period interest-only payment
During the draw period, minimum payments are usually interest only—you pay the interest that accrues each month, but nothing goes toward the principal yet.
Simple method
Monthly payment = (Balance × Annual rate) ÷ 12
Example: ($50,000 × 8%) ÷ 12 = $333/month
Precise (daily rate) method
Daily rate = Annual rate ÷ 365
Monthly payment = Balance × daily rate × days in month
Example: $50,000 × (0.08 ÷ 365) × 30 = $329/month
The simple method is close enough for planning. Lenders generally use the daily rate method, which is why your statement may show a slightly different number.
Credit line vs. drawn balance: Approved for $75,000 but drew $50,000? Your payment is based on $50,000—not $75,000. As you draw more, the payment rises. Draw the full $75,000 and your interest-only payment at 8% becomes $500/month.
One more lever many borrowers skip: paying down principal during the draw period. Many lenders don’t require it. But doing so reduces your balance before repayment begins, which could lead to a lower repayment payment and less total interest. It is one of the most useful levers on a HELOC that many people do not use.
How to calculate your repayment period payment
The repayment period—typically 10-20 years—is when your payment typically shifts to cover both principal and interest.
Let's revisit our example: Same $50,000 balance and 8% rate. Different phases.
| Repayment term | Monthly payment |
|---|---|
| 20-year term | $418/month |
| 10-year term | $607/month |
After the draw period, payments went from $333/month to $418 or $607—same balance, same rate. The difference is amortization: the loan math that spreads principal repayment across your remaining term. This is not a penalty or a fee. It is just the math of paying back what you borrowed.
The term length matters. A $50,000 balance at 8% costs $189/month more on a 10-year term than a 20-year term. In other words, for another $189 per month, you cut the repayment term in half. Some lenders offer both. Confirm which applies to your loan before your draw period ends. The longer you take to repay the debt, the more interest you’ll pay.
When repayment starts: the month after your draw period ends. Draw period ends in October? First principal and interest payment is due in November.
HELOC payment examples at common loan amounts
If you want to skip the formula and see what HELOC payments could look like at common loan amounts, here is the breakdown. All examples use 8% APR for illustration.
| Loan amount | Draw payment (interest only) | Repayment (P+I, 20yr) | Repayment (P+I, 10yr) |
|---|---|---|---|
| $30,000 | $200/month | $251/month | $364/month |
| $50,000 | $333/month | $418/month | $607/month |
| $100,000 | $667/month | $836/month | $1,213/month |
The draw period payment may be manageable. But be sure to factor the higher payments into your budget, too.
How variable rates affect your HELOC payment
Most HELOCs carry a variable rate. That’s a rate that can change over time, generally tied to the Prime Rate. The Prime Rate is a rate that banks follow. When the Prime Rate changes, your HELOC payment could change with it, sometimes within the same billing cycle.
Lenders add a certain amount on top of the Prime Rate to set your personal rate. Your loan agreement might say that your rate is “Prime plus 2%,” and so on.
Here is what a $50,000 balance costs at different interest rates:
| Rate | Draw payment (interest only) | Repayment (P+I, 20yr) |
|---|---|---|
| 7% | $292/month | $388/month |
| 8% | $333/month | $418/month |
| 9% | $375/month | $450/month |
A 2% rate increase adds about $83/month during the draw period on a $50,000 balance. That's a lot—but potentially manageable if you run the scenarios in advance and know what to expect.
Don't forget the lifetime rate cap. Most HELOCs have one. Even if the Prime Rate spikes, your rate legally cannot exceed the cap written into your loan documents. Find that number before you accept the loan.
Some lenders also offer a fixed-rate conversion option—the ability to lock part or all of your balance into a fixed rate during the draw period. Not all lenders offer it, but it is worth asking about if rates are rising.
Use the HELOC calculator to run your numbers
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Use your actual drawn balance—not your full credit line. Your current rate is on your most recent statement, listed as index + margin. Have your draw period end date and repayment term ready.
Bills Action Plan
- Step 1: Find your two numbers. Calculate your draw period payment (balance × rate ÷ 12) and your repayment period payment. Plan your budget around the higher one, not the lower one.
- Step 2: Check your repayment term. A 10-year and 20-year term produce very different monthly payments on the same balance. Confirm which term you have. It's in your loan agreement.
- Step 3: Look up your rate cap. It's in your loan documents. That number is the ceiling on your worst-case payment. It's worth knowing before rates move.
Key terms
| Term | Definition |
|---|---|
| Draw period | The phase when you can borrow from your HELOC—typically 10 years. Minimum payments are usually interest only. |
| Repayment period | The phase after the draw period when you repay principal + interest. Typically 10-20 years depending on your loan. |
| Interest-only payment | A payment covering only the interest that accrued—nothing reduces the balance. |
| Amortization | Repaying a loan in equal installments that cover both principal and interest over a set term. |
| Prime Rate | A benchmark rate that moves with the federal funds rate. Most HELOC rates are Prime Rate + lender's margin. |
| Variable rate | A rate that can change over time. Most HELOCs are variable—your payment can go up or down. |
| Rate cap | The maximum interest rate your HELOC can reach, regardless of how high the Prime Rate climbs. Set in your loan agreement. |
| Balloon payment | A large lump-sum payment due at the end of a loan term. Some HELOCs require this if you have not paid down principal during the draw period. |
What is the monthly payment on a $100,000 HELOC?
At 8% APR, a $100,000 HELOC could cost roughly $667/month in interest during the draw period. When repayment begins on a 20-year term, that could rise to about $836/month—or $1,213/month on a 10-year term. Your actual payment depends on your rate at the time of repayment, how much you have drawn, and the repayment term in your loan agreement.
What happens to my HELOC payment when the draw period ends?
Your payment generally increases—sometimes significantly. During the draw period, you might be required to pay interest only. In that case, when repayment begins, your payment shifts to cover both principal and interest on your full outstanding balance. On a $50,000 balance at 8%, that jump is from $333/month to $418/month on a 20-year term, or $607/month on a 10-year term. Repayment begins the month after your draw period ends.
Some lenders require a principal plus interest payment. In that case, your payment will be based on how much you owe during the draw period and the repayment period.
Should I pay down principal during the draw period?
You might not be required to, but it is worth considering. Paying principal during the draw period reduces your balance before repayment begins, which means lower payments later and less total interest paid. Even modest extra payments could make a meaningful difference compounded over a 10-year draw period.
When do I start paying back a HELOC?
You start paying interest when you draw from the line—not when the account is opened. Principal repayment begins when your draw period ends, typically 10 years from origination. Check your loan agreement for your exact repayment start date.