HELOC Payment Calculator
Calculate your Home Equity Line of Credit payment in both of its phases — interest-only during the draw period, fully amortizing during repayment — and see the payment-shock jump between them. This is the payment-side calculator; for the separate question of how much HELOC interest you can deduct, see the HELOC Interest Deduction Calculator.
The amount you've actually borrowed against the line — not your total credit limit.
HELOCs are typically variable-rate, indexed to the prime rate plus a lender margin — enter your current rate; it will reset periodically.
Interest-only period — commonly 10 years.
Fully-amortizing period once the draw period ends — commonly 15 or 20 years.
Draw-Period Payment
$333.33Interest-only
Repayment-Period Payment
$477.83Fully amortizing
Payment Shock
+$144.4943% increase at transition
| Phase | Length | Monthly Payment | Total Interest |
|---|---|---|---|
| Draw (interest-only) | 120 mo | $333.33 | $40,000 |
| Repayment (amortizing) | 180 mo | $477.83 | $36,009 |
| Total (both phases) | 300 mo | — | $76,009 |
| Year | Interest | Principal | Balance |
|---|---|---|---|
| 1 | $3,935 | $1,799 | $48,201 |
| 2 | $3,786 | $1,948 | $46,253 |
| 3 | $3,624 | $2,110 | $44,143 |
| 4 | $3,449 | $2,285 | $41,858 |
| 5 | $3,259 | $2,475 | $39,383 |
Assumes the drawn balance stays fixed (no further draws or paydowns) through the draw period and that your rate stays constant through repayment — in reality a HELOC's variable rate can reset periodically, changing both figures. Confirm your exact draw/repayment structure with your lender.
Edit inputs ↑Two phases, two very different payments
A HELOC is structured in two distinct phases. During the DRAW PERIOD (commonly 10 years), you can borrow up to your credit limit as needed, and your required payment is interest-only — $333.33/month on a $50,000 balance at 8%. None of that payment reduces what you owe; the balance stays flat unless you voluntarily pay down principal.
Once the draw period ends, the REPAYMENT PERIOD begins (commonly 15-20 years) and the line converts to a standard fully-amortizing loan on whatever balance remains — $477.83/month on that same $50,000 balance over 15 years. Over the full life of the line, total interest comes to $76,009 — $40,000 during the interest-only draw period and $36,009 during repayment.
Because a HELOC's rate is variable, both figures move with the market — this calculator holds your entered rate fixed across both phases as an estimate. Check your loan documents for your specific margin over prime and any periodic/lifetime rate caps.
Avoiding payment shock
- Pay down principal during the draw period. Even modest extra payments while you're only required to pay interest reduce the balance the repayment-phase amortization starts from.
- Know your conversion date. HELOC draw periods end on a fixed schedule, not gradually — mark the date and budget for the new payment well ahead of time.
- Ask about a fixed-rate lock option. Some lenders let you convert some or all of the balance to a fixed rate before or at the start of repayment, trading rate flexibility for payment certainty.
- Consider refinancing into a fixed second mortgage or a cash-out refinance before the draw period ends if the projected repayment-phase payment doesn't fit your budget.
Frequently asked questions
Why does my HELOC payment jump so much when the draw period ends?
During the draw period you typically only pay interest — none of the payment reduces the balance. Once repayment begins, the same balance has to be fully paid off (principal + interest) over the repayment window, so the payment has to be much larger. On a $50,000 balance at 8%, the interest-only payment is $333.33/month; a 15-year repayment period on the same balance is $477.83/month — a $144.49 jump. Lenders call this "payment shock," and it's the single most common HELOC surprise.
Why is my HELOC rate variable?
Most HELOCs are indexed to the prime rate (published by major banks and tracked by the Federal Reserve) plus a lender-set margin, and they reset periodically — often monthly. That means both your interest-only draw payment and your eventual repayment payment can move with the broader rate environment, unlike a fixed-rate home equity loan or a fixed-rate first mortgage.
Can I pay down principal during the draw period?
Yes — most HELOCs allow (but don't require) principal payments during the draw period. Any principal you pay down during the draw period reduces both your interest-only payment immediately and your eventual repayment-phase payment, since the repayment amortization is based on whatever balance remains when the draw period ends.
Is HELOC interest tax deductible?
Only conditionally. Since the 2017 Tax Cuts and Jobs Act (made permanent by the 2025 One Big Beautiful Bill Act), HELOC interest is deductible only when the funds are used to buy, build, or substantially improve the home securing the loan — not for debt consolidation, tuition, or general spending. See the HELOC Interest Deduction Calculator linked above for the itemized-deduction math.
Sources
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