HELOC Calculator

Interest-only payments are balance × (annual rate ÷ 12). On a $100,000 balance at 9%, that is $100,000 × 0.09 ÷ 12 = $750 per month, and the principal balance stays exactly where it started. Rule of thumb: every $10,000 of balance adds $8.33 per month for each 1 percentage point of rate.

The outstanding balance is re-amortized over the repayment period (commonly 10-20 years), so you begin paying principal and interest every month. On $100,000 at 9% over 20 years the payment goes from $750 to about $899.73 — roughly a 20% jump. Shorter repayment terms or higher balances make the shock bigger, which is why borrowers often prepay principal during the draw.

Both phases count. A full $100,000 draw at a constant 9% with a 10-year interest-only draw accrues $90,000 of interest ($750 × 120 months), then the 20-year repayment adds about $115,934 — roughly $205,934 total over 30 years. Because none of the principal is retired during the draw, long interest-only phases are expensive; paying principal early is the biggest lever you control.

Almost certainly not. HELOC rates are variable — usually the prime rate plus a margin set by your lender — and they can change as often as monthly. This calculator holds the rate constant across both phases so you get a clean baseline. To stress-test, rerun it a point or two higher: each 1-point move changes the interest-only payment by $8.33/month per $10,000 drawn, and raises the amortized repayment payment too.

A HELOC is a revolving line with a variable rate: borrow as needed, usually interest-only during the draw — best for flexible or phased spending like renovations. A home equity loan is a fixed-rate lump sum with a fixed monthly payment — best when you know the exact cost and want rate certainty. If rates are rising, the fixed loan locks your cost; if they are falling, the HELOC can get cheaper over time.