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Interest-Only HELOC Calculator
During the HELOC draw period, the minimum monthly payment at most lenders is interest only. The formula is balance times rate divided by 12. At the May 2026 national average rate of 7.02%, that is $58.50 per month per $10,000 borrowed.
Per-$10,000 monthly cost by rate
6.00%
$50.00
6.50%
$54.17
7.02%
$58.50
7.50%
$62.50
8.00%
$66.67
9.00%
$75.00
The arithmetic and why it matters
The interest-only payment formula on a HELOC is unusually simple compared to most consumer loan math. Take the outstanding balance, multiply by the annual percentage rate, divide by twelve. The result is the minimum payment due in the next billing cycle. Because the rate is variable on most HELOCs (prime plus margin, updated within one billing cycle of any Federal Reserve H.15prime-rate change), the payment recalculates every month based on the current rate and the current balance. A borrower whose balance grew from $50,000 to $80,000 over the past month will see a corresponding increase in next month's interest payment.
The simplicity hides a real risk: interest-only payments do not reduce the principal balance. Ten years of paying the minimum on a $100,000 line means you owe $100,000 plus accumulated interest at the transition to the repayment period. Borrowers who treat the interest-only payment as "my HELOC payment" without understanding it does not reduce the balance often experience the repayment-phase amortizing payment as a sudden 33% increase in their monthly housing cost. The CFPB documents this outcome in their HELOC consumer-protection guidance and recommends voluntary principal payments during the draw period as the single most effective behavioural change to reduce long-term borrowing cost.
The interest-only structure also creates a specific tax pattern. Interest paid on HELOC funds used to buy, build, or substantially improve the home that secures the loan is deductible under IRS Publication 936, subject to itemization and the $750,000 combined-debt cap. Because interest-only payments are entirely interest, the entire payment is potentially deductible in the year paid. Borrowers in higher tax brackets receive a meaningful after-tax benefit; borrowers who do not itemize (the majority of US taxpayers post-TCJA) receive no tax benefit and bear the full interest cost.
Interest-only payment by balance and rate
| Balance | 6.0% | 7.02% | 8.0% | 9.0% | 10.0% |
|---|---|---|---|---|---|
| $25,000 | $125 | $146 | $167 | $188 | $208 |
| $50,000 | $250 | $293 | $333 | $375 | $417 |
| $75,000 | $375 | $439 | $500 | $563 | $625 |
| $100,000 | $500 | $585 | $667 | $750 | $833 |
| $150,000 | $750 | $878 | $1,000 | $1,125 | $1,250 |
| $200,000 | $1,000 | $1,170 | $1,333 | $1,500 | $1,667 |
| $250,000 | $1,250 | $1,463 | $1,667 | $1,875 | $2,083 |
| $500,000 | $2,500 | $2,925 | $3,333 | $3,750 | $4,167 |
When interest-only makes financial sense
Interest-only payments are mathematically appropriate in three specific scenarios. First, when the borrower has a high-confidence expectation of a future lump-sum payoff: an upcoming property sale, an asset liquidation, a deferred compensation vesting, an inheritance, or a known business exit event. Paying only the interest preserves the borrower's liquidity to deploy elsewhere until the lump sum arrives. Second, when the borrower has a confirmed investment opportunity earning more than the HELOC after-tax cost (rare in 2026 with prime at 7.50% and HELOC rates around 7.02%, since most fixed-income investments yield less and equities have higher risk). Third, when the borrower has a near-term cash-flow crunch (medical event, employment transition, family emergency) and the interest-only payment keeps housing costs manageable while other parts of the financial picture stabilize.
Outside those scenarios, interest-only payments are usually a slow leak in the household balance sheet. Every month of paying only interest is a month of borrowing cost without corresponding equity rebuild. The behaviour pattern that does work for most borrowers is to pay the interest-only minimum officially and then voluntarily add a principal-pay-down amount based on the household budget. This approach preserves the contractual flexibility (if a tough month happens, you can drop to the minimum) while making real progress against the balance during normal months.
A common mistake is to keep a HELOC balance interest-only because the rate is "low" relative to credit cards. The comparison is misleading: the HELOC rate is genuinely lower than credit-card APRs, but the HELOC is secured by your home, while credit-card debt is not. Carrying a $50,000 HELOC balance at 7.02% for 10 years pays $35,100 in interest cost; the same $50,000 paid off over 5 years would cost only $9,400 in interest. The lower rate makes the carrying cost more tolerable but it does not make indefinite carrying cost desirable.
Variable rate and interest-only payment volatility
Because the HELOC rate is variable and the interest-only payment formula directly multiplies the rate by the balance, the interest-only payment can swing significantly across a Federal Reserve rate cycle. On a $100,000 balance, a swing from 7.00% to 8.00% raises the interest-only payment from $583 to $667 per month. A swing to 9.00% raises it to $750. A swing to 10.00% (last seen in the early 2000s) raises it to $833. The lifetime cap disclosed under Reg Z 1026.40 (typically 18%) sets the contractual maximum at $1,500 per month for the $100,000 balance, though rate paths that reach 18% are historically rare.
The volatility matters for borrowers using the interest-only payment as a baseline budget item. A household that built a budget around $585 per month interest cost and saw the payment jump to $667 during a Fed tightening cycle may face cash-flow strain. Two mitigations: maintain a 6-month emergency reserve sized to cover the worst-case interest cost at the lifetime cap, or pay down the balance during low-rate periods to reduce the principal that the variable rate is multiplied against. Both reduce interest-payment volatility without requiring any prediction about Fed policy.
A subset of lenders offer convert-to-fixed features on their HELOC products (PNC Choice HELOC is the most prominent example). The borrower can convert all or part of the outstanding balance to a fixed rate, locked at the rate available at the time of conversion. This locks in the interest cost on the converted portion but typically removes the interest-only payment option (the fixed-rate portion amortizes immediately). The trade-off between rate certainty and payment-structure flexibility is specific to each borrower's situation; for a borrower who already plans to retire the balance, the fixed-rate convert is usually attractive.
Frequently asked questions
How is interest-only HELOC payment calculated?
The formula is the outstanding balance multiplied by the annual percentage rate, divided by 12. For example, $80,000 outstanding at 7.02% APR equals $80,000 times 0.0702 divided by 12, which equals $468 per month. The balance does not reduce because none of the payment goes to principal.
Is interest-only the minimum payment on every HELOC?
On most US HELOCs during the draw period, yes. A minority of lenders (some credit unions, some convert-to-fixed product variants) require a small principal component on top of interest, typically 1% to 2% of the outstanding balance. Always read the Reg Z 1026.40 disclosure for the exact minimum payment formula.
Can I pay only the interest for the entire 10-year draw period?
Yes at almost every US HELOC lender. The line requires only the interest-only minimum during the draw period. Doing so means the balance stays constant: you do not build equity through repayment during these 10 years. When the repayment period begins, the full balance amortizes from day one, producing the standard payment shock.
What is the total cost of paying interest-only?
Holding a $100,000 balance at 7.02% for 10 years generates $70,200 in interest paid. Adding the 20-year amortizing repayment phase at the same rate produces an additional $86,300 in interest, totaling $156,500. The same $100,000 balance retired over the 10-year draw period (paying principal too) would cost only $39,400 in total interest.
When does paying interest-only make sense?
Three scenarios. First, when the borrower expects a future windfall (bonus, asset sale, inheritance) that will retire the balance in a lump sum. Second, when interest paid on the line is fully tax-deductible (used for home improvement) and the tax benefit covers part of the interest cost. Third, when the borrower has a clear investment opportunity earning more than the HELOC rate net of tax, making the spread profitable.
How much does an extra principal payment save me?
On a $100,000 balance at 7.02%, paying an extra $200 per month during the draw period reduces the balance entering repayment from $100,000 to $66,400. That cuts the amortizing payment from $776 to $515 per month (a $261 monthly saving) and reduces total lifetime interest by $43,000.