Direct answer
A simple monthly planning estimate is outstanding balance x annual rate / 12. Actual HELOC interest calculations and minimum payments vary by lender agreement.
Published and reviewed October 3, 2026. Borrow Home Equity is not a lender. This page is educational and does not guarantee approval, rates, terms, or available funds.
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Simple monthly formula
For planning, monthly interest-only estimate = outstanding drawn balance x annual interest rate / 12. This approximation does not include principal repayment, fees, daily accrual differences, or lender minimums.
Worked examples
If the drawn balance is $50,000 and the illustrative annual rate is 8.00%, the monthly interest-only estimate is $333.33. If the same balance used 10.00%, the estimate would be $416.67. These are examples only.
| Drawn balance | Illustrative annual rate | Monthly interest-only estimate | Annual interest amount |
|---|---|---|---|
| $25,000 | 8% | $166.67 | $2,000.00 |
| $50,000 | 8% | $333.33 | $4,000.00 |
| $50,000 | 10% | $416.67 | $5,000.00 |
| $75,000 | 9% | $562.50 | $6,750.00 |
Variable rate concept
Many HELOCs use variable rates. A variable rate may be described as a benchmark or index plus a margin, but the exact formula and adjustment rules are set by the lender agreement.
Methodology and limitations
The examples use balance x annual rate / 12. They are not current market rates, APRs, lender quotes, or approval criteria. Borrow Home Equity does not set HELOC rates.
Authoritative sources
- CFPB: What you should know about home equity lines of credit
- CFPB Regulation Z: home equity plan disclosures
Frequently Asked Questions
What balance is used for HELOC interest?
Interest is generally tied to the outstanding drawn balance, not the unused credit line, but agreement terms vary.
Is APR the same as the simple interest rate?
Not necessarily. APR and disclosed cost terms can include rules or costs beyond a simple interest calculation.
Does a variable HELOC rate change every month?
Adjustment timing and limits depend on the agreement.