The 30-second answer
HELOC payments come in two phases. During the draw period (typically 10 years) most HELOCs allow interest-only payments: balance × rate ÷ 12. During the repayment period (typically 10-20 years after the draw ends) payments jump to full principal-and-interest amortization. On a $50,000 balance at 8.5%, that's $354/month interest-only during the draw period and $620/month fully amortizing during 10-year repayment — a payment jump of roughly 75%.
For exact numbers on your specific balance and rate: use our full HELOC payment calculator or the HELOC vs cash-out refinance calculator. Both handle the full amortization automatically.
The draw period formula
Most HELOCs are interest-only during the draw period. The formula is simple:
Monthly interest-only payment = Outstanding balance × (Annual rate ÷ 12)
Example: $75,000 outstanding at 8.5% APR:
$75,000 × (0.085 ÷ 12) = $75,000 × 0.007083 = $531.25/month
Note that this only covers interest. Your balance stays at $75,000 forever unless you pay additional principal. Many borrowers use HELOCs this way for years, then get surprised when the draw period ends.
Draw-period payments across common balances (8.5% APR)
| Outstanding balance | Interest-only monthly payment | Annual interest cost |
|---|---|---|
| $25,000 | $177 | $2,125 |
| $50,000 | $354 | $4,250 |
| $75,000 | $531 | $6,375 |
| $100,000 | $708 | $8,500 |
| $150,000 | $1,063 | $12,750 |
| $200,000 | $1,417 | $17,000 |
| $300,000 | $2,125 | $25,500 |
Adjust proportionally for your actual rate. At 7.5% multiply by 7.5/8.5 (about 0.88); at 9.5% multiply by 9.5/8.5 (about 1.12).
The repayment period formula
Once the draw period ends, the HELOC converts to a standard amortizing loan. Your remaining balance is paid off over the repayment period (typically 10-20 years) using the standard mortgage payment formula:
Monthly P&I payment = P × [r(1+r)^n] / [(1+r)^n - 1]
Where: P = balance, r = monthly rate (APR/12), n = number of monthly payments
Example: $50,000 balance at 8.5% over 10-year repayment:
r = 0.085/12 = 0.007083
n = 120
Monthly payment = $619.96
You don't need to run this manually — it's the standard loan calculation any calculator does. But knowing the formula helps you sanity-check what a lender quotes.
Repayment-period payments (10-year repayment, 8.5% APR)
| Balance at start of repayment | Monthly P&I payment | Total interest over 10 years |
|---|---|---|
| $25,000 | $310 | $12,204 |
| $50,000 | $620 | $24,408 |
| $75,000 | $930 | $36,612 |
| $100,000 | $1,240 | $48,816 |
| $150,000 | $1,860 | $73,224 |
| $200,000 | $2,480 | $97,632 |
Repayment on a 20-year term is roughly 40% cheaper monthly than 10-year but nearly doubles total interest. If your goal is minimum monthly payment during repayment, take the longer term. If your goal is minimum total interest, take the shorter one.
The payment jump that catches borrowers off-guard
The single most important number in HELOC planning is the ratio between your interest-only draw payment and your repayment-period P&I payment. On the same $50K balance at 8.5%:
- Draw period interest-only: $354/month
- Repayment period P&I (10 years): $620/month
- Payment jump: +$266/month (+75%)
Borrowers who've been paying $354/month for a decade and then get a $620 bill in month 121 often can't absorb the increase. That's the mechanism behind most HELOC repayment defaults.
The prevention is simple: pay principal during the draw period even when the lender only requires interest. Every dollar you pay toward principal during the draw period shrinks the eventual repayment payment. Pay $354 (interest) plus another $200-$300 toward principal each month and by the time repayment starts, you've knocked down the balance enough that the P&I payment isn't a shock.
Total interest paid across the life of a HELOC
Here's what a $75,000 HELOC actually costs over 30 years (10-year interest-only draw + 20-year repayment) at 8.5%, under three scenarios:
| Scenario | Total interest paid | Time to full payoff |
|---|---|---|
| Interest-only during draw, full 20-yr repayment | ~$120,000 | 30 years |
| Interest + $250/mo extra principal during draw, then repayment | ~$78,000 | ~24 years |
| Interest + $500/mo extra principal during draw, then repayment | ~$47,000 | ~18 years |
| Full amortization from day 1 (like a home equity loan) | ~$52,000 | 15 years |
Notice the range: the same $75,000 loan can cost anywhere from $47,000 to $120,000 in total interest depending on how the borrower manages payments during the draw period. Nothing else in the HELOC — rate, closing costs, term — moves total lifetime cost as much as your draw-period payment discipline.
How rising rates affect your payment
HELOCs are variable-rate. If Prime rises 1 percentage point, your rate rises 1 point, and your payment rises proportionally. Illustrating on $50,000 balance:
| Rate | Interest-only payment (draw) | P&I payment (10-yr repay) |
|---|---|---|
| 7.5% | $313 | $594 |
| 8.5% (today) | $354 | $620 |
| 9.5% | $396 | $647 |
| 10.5% | $438 | $675 |
| 11.5% | $479 | $703 |
The good news: on interest-only payments, a 1-point Prime move changes the monthly payment by about 12%. On amortizing payments during repayment, the same move changes the payment by 4-5%. Variable rate risk is real but not usually catastrophic in single-year moves.
Use the interactive calculators for exact numbers
The tables above are useful for rough planning. For exact numbers tuned to your specific rate, balance, draw and repayment terms, use our interactive tools:
- Full HELOC payment calculator — enter your line size, rate, and terms; get interest-only draw payments, P&I repayment payments, and total interest.
- HELOC vs cash-out refinance calculator — side-by-side comparison of HELOC and cash-out refi economics for your specific numbers.
Both calculators use the standard financial formulas above with proper amortization schedules — no marketing shortcuts, no hidden assumptions.
The most useful rule of thumb
If you want a single number to plan around: a HELOC costs roughly $60-$70 per month per $10,000 of balance during the draw period, and roughly $120-$130 per month per $10,000 of balance during 10-year repayment. These estimates work across the typical 2026 HELOC rate range and give you a starting point without needing to run formulas.
On $85,000: $510-$600/month interest-only, $1,020-$1,105/month during repayment. Close enough for back-of-napkin decisions.
Get your actual HELOC rate — then plug the real number into the calculator
Rate estimates are useful; a real rate quote is better. Free, soft-pull only, takes about five minutes. Once you have your quoted rate, our calculator will show your exact payment.
FAQ
How do I calculate my HELOC monthly payment?
Draw-period interest-only: balance × rate ÷ 12. Repayment-period P&I: use the standard mortgage formula or an amortization calculator.
What's the difference between draw and repayment period payments?
Draw is interest-only (payment is lower, no principal reduction). Repayment is fully amortizing (payment is higher, includes principal). The jump from draw to repayment can be 60-100%.
How much does a HELOC cost total over its life?
Depends heavily on draw-period payment discipline. Same $75K loan can cost $47K to $120K in total interest depending on whether you pay principal during the draw period.
Should I make interest-only or principal payments during the draw period?
Almost always principal if you can afford it. It reduces the payment shock at repayment start and cuts total lifetime interest substantially.
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