Reference formulas and worked examples below keep their stated units. Monetary examples use USD; dimensional examples use US customary units unless labeled otherwise. Metric calculator inputs are converted to these reference units before calculation. Choosing another currency does not convert example amounts or exchange money.
How to use this heloc calculator
Each planned draw occurs at the beginning of its month. Draw-period payments cover that month’s interest only. The ending balance is then amortized over the repayment period.
How the calculation works
At the start of each draw month, add the planned new borrowing to the balance. Charge monthly interest at draw rate ÷ 1,200, rounded to cents. Paying exactly that interest leaves principal unchanged during the draw phase.
Balance at repayment = initial balance + monthly new borrowing × draw months. The plan is rejected if it exceeds the entered credit limit.
At repayment, calculate a fixed monthly amortizing payment using the repayment rate and remaining term. Payments cover interest and principal; the last payment adjusts for cent rounding. At zero interest, principal is divided by the term.
Total cash paid = draw-period interest + repayment payments + entered upfront cash fees. Borrowing received is shown separately and is not treated as a payment.
Worked example
Begin with 10,000 drawn, add 1,000 at the start of each of two months, and use a 12% annual draw rate. The first interest-only payment is 110 and the second is 120. The repayment balance is 12,000. If the repayment rate is 0% for 12 months, payments become 1,000, and total interest for both phases is 230.
Limits and assumptions
This is a fixed monthly model with interest rounded to cents. Daily balance calculations, payment dates, changing rates, promotions, taxes and jurisdiction-specific contract rules are not inferred. This model selects an interest-only draw phase followed by fully amortizing repayment. It excludes variable-rate resets within a phase, interest capitalization, principal payments during drawing, irregular advances, annual fees, early-closure penalties, balloons, collateral qualification and foreclosure risk assessment.
Frequently asked questions
Why does the payment rise when the draw period ends?
The repayment phase starts paying down principal as well as interest. Its interest rate can also differ in this scenario.
What happens if borrowing exceeds the limit?
The monthly borrowing field is marked for correction. The model does not quietly cap your planned draws.
Can I model a HELOC already in repayment?
Yes. Enter the current balance, set draw months to zero, and use the remaining repayment rate and term.
Does this predict variable HELOC rates?
No. Each phase uses one editable constant rate. Try separate scenarios rather than treating the default as a forecast.
Are fees added to the balance?
The entered upfront fees are cash-paid. They increase total outlay but not principal or the credit-limit usage.