How much you can borrow against your home, what a draw costs during the interest-only years, and the payment jump when repayment begins.
Most lenders cap mortgage + HELOC at 80–85% of the home's value.
HELOC rates are variable (prime + margin); this models it as fixed.
"Principal too" pays as if amortizing over the full draw + repayment span, which avoids the payment jump.
This HELOC calculator estimates your available credit line from your home value and existing mortgage, the interest-only payment while you draw on the line, and the larger fully amortizing payment that kicks in once the repayment period starts.
Your borrowing limit is your home's value times the lender's combined loan-to-value cap (often 80–85%) minus what you still owe on the first mortgage. During the draw period you typically pay interest only on what you've borrowed, so the payment is simply the balance times the monthly rate. When the repayment period begins you can no longer draw, and the balance amortizes — which is why payments often jump sharply.
Lenders typically let you borrow up to a combined loan-to-value of 80–85% of your home's value, minus what you still owe on the first mortgage.
You can no longer borrow, and the loan converts to a repayment schedule of principal plus interest. Payments often jump sharply at this point.
HELOCs usually carry a variable rate applied to your outstanding balance, so interest accrues only on what you have actually drawn.
A HELOC is a revolving line you draw from as needed, usually at a variable rate. A home equity loan is a lump sum at a fixed rate. This calculator models the HELOC's draw-then-repay structure.
During the draw period you often pay only interest, so the principal never shrinks. Once repayment starts, that full principal amortizes over the remaining years, which can roughly double the payment.
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