Calculator inputs
Example data table
| Scenario | Limit | Balance | Rate | Method | Fees | Days | Month 1 payment (approx) |
|---|---|---|---|---|---|---|---|
| Sample A | 50,000 | 20,000 | 9.25% | Daily / 365 | 10 monthly + 50 annual | 30 | ~ 171.23 |
| Sample B | 100,000 | 65,000 | 10.50% | Monthly simple | 0 monthly + 0 annual | — | ~ 568.75 |
Formula used
Monthly payment ≈ Interest + Fees (+ one-time fees). This calculator also supports optional extra principal, which reduces future interest.
Interest = Balance × (APR/100) × (Days in Month ÷ Day-Count Basis). Choose a basis of 365 or 360 to match your lender’s convention.
Interest = Balance × (APR/100) ÷ 12. This is a common approximation when daily details are not required.
Utilization (%) = Ending Balance ÷ Credit Limit × 100. Higher utilization can affect pricing and underwriting outcomes.
How to use this calculator
- Enter your credit limit and current balance.
- Select rate mode: direct, or index plus margin.
- Choose daily or monthly interest calculation method.
- Set fees, including annual or one-time setup fees.
- Add planned monthly draws and optional extra principal.
- Click Calculate to see results above the form.
- Download CSV or PDF to share your projection.
Payment and balance trend
Payment drivers during an interest-only period
Interest-only lines typically require payment of accrued interest plus any recurring charges. If your balance is 20,000 at 9.25% APR and your lender uses a 365-day basis, a 30-day month produces interest near 152.05. Add a 10 monthly fee and an annual fee spread across months to reach a realistic all-in payment.
Daily interest versus simple monthly interest
Many HELOC statements compute interest daily using the outstanding balance and a day-count convention. This calculator lets you choose 365 or 360 to mirror your agreement. The monthly method is a fast approximation for budgeting, but can differ when balances change mid-month due to draws or principal payments.
Utilization and borrowing capacity signals
Utilization is ending balance divided by credit limit. A 50,000 limit with a 35,000 balance is 70% utilization. Tracking this percentage helps you anticipate lender actions such as rate tiers, line management decisions, or tighter underwriting on future credit requests. The schedule shows utilization each month as draws accumulate.
Planning draws to manage cash flow
If you plan a 1,000 monthly draw for renovations, the payment rises as the balance grows. Use the projection months, monthly draw, and extra principal fields to compare strategies. Even a small extra principal payment, like 100 per month, reduces future interest because interest is calculated on the remaining balance.
Turning projections into shareable reports
Budget discussions often require clarity across stakeholders. Export the schedule as CSV to audit month-by-month numbers in a spreadsheet, or download the PDF summary for quick sharing. Pair the chart with the table to validate assumptions and keep your plan aligned with lender disclosures and fee schedules.
FAQs
During the interest-only period, the required payment typically covers accrued interest and fees. Principal repayment is optional unless your agreement specifies minimum reductions or end-of-draw rules.
Some lenders apply a 360-day convention for daily interest. It slightly increases per-day interest versus 365. Choose the basis that matches your disclosure or statement calculations.
It is a budgeting shortcut: balance × APR ÷ 12. It can diverge from daily interest when balances change within a month, or when lenders use different day-count rules.
Fees do not change the APR, but they raise your total cost. This calculator adds recurring and one-time fees to show a more realistic payment and a blended annualized cost estimate.
A higher balance produces more interest. If you add monthly draws, the schedule increases interest and payment as the balance grows, capped by the credit limit.
Use it to compare scenarios, not as a final offer evaluation. Confirm APR, fees, and day-count details with lender documents, and consider taxes and closing costs separately.