Monthly interest estimate, then hypothetical repayment
A US HELOC may permit interest-only payments during the draw period, then amortize the remaining balance or require a balloon after the draw period. This page divides the current annual rate by 12 for a monthly interest estimate and separately amortizes today’s balance at that same frozen rate. Actual statements may calculate interest from daily balances and billing-cycle days, and a lender’s minimum-payment rule may include principal or fees. The mortgage page amortizes a purchase; remaining-loan-balance follows an existing fixed schedule.
Repayment estimate = amortizing payment of today’s balance at today’s rate over the entered months
At 0%, monthly interest is $0 and repayment is balance ÷ months
Example
A $50,000 drawn balance at 8.5% produces a simple monthly interest estimate of $354.17. Amortizing that same $50,000 at an unchanged 8.5% over 20 years is about $433.91 a month. A $120,000 balance at 8.25% produces an $825 monthly interest estimate.
What this estimate leaves out
The repayment term must resolve to a whole number of months. Daily accrual, statement length, minimum-payment formulas, rate resets, caps, floors, introductory rates, fees, future draws, and balloon repayment are not modeled. Compare the result with the statement and plan disclosures.