HELOC Calculator: Borrowing Limit and Monthly Payments
This HELOC calculator turns your lender's CLTV and secured debt into a room-to-borrow estimate, then models payments on your draw at one fixed rate.
What This Calculator Does
You get two separate answers here. First, extra borrowing room, from the home value you enter, your lender's CLTV and the existing secured debt that lender counts. Second, payments on the principal you request: interest only on a flat balance, then full monthly amortization, same rate throughout. None of these outputs is home equity, approved credit or cash in hand, and none predicts upcoming variable-rate bills.
Who Is This For
Checking a defined HELOC scenario in Florida, as an owner or an agent? Get these confirmed by the lender: how it counts debt, the CLTV, charges, rate and phase terms. Textbook ratios and market averages shouldn't stand in for them. Your current mortgage payments stay outside every HELOC figure here.
How It Works
Enter the home's value, your lender's CLTV cap, every existing debt secured by the property that the lender counts, and the amount you want to draw. If the draw is above 0, add the rate, 0–50 whole interest-only years and 1–50 whole repayment years. If it's 0, skip the rate and periods. Setting interest-only years to 0 starts repayment at once. Then read the capacity, the room left or excess (signed + or −), the monthly payment for each phase and the totals. To test another case, edit only real numbers and rerun.
Frequently Asked Questions
Can I read the HELOC calculator's capacity as my home equity or approved credit?
No. It's a scenario estimate of capacity, not your real home equity, an underwriting result or a lender commitment. To get it, multiply the home value by the CLTV you typed, drop any fraction of a cent, then take away the secured debt your lender counts. A result under zero shows as zero. That debt means every loan or line on the property by the lender's method, not just the first mortgage, plus full line commitments if the lender includes them. The tool assumes no standard 85% rule.
If my line is bigger than my draw, which one sets the payment?
Only the principal you request. The model treats that amount as borrowed from the start and leaves it untouched for every interest-only payment, so the draw drives the payment, not the line. If you finance charges into the principal, put them in the number; the principal isn't the cash you receive. Not modeled: extra draws, paydowns during the draw phase, a revolving transaction history. When repayment begins, the whole principal amortizes.
Will a fixed-rate result stop my payments from rising later?
No. A scenario with a constant rate is not a future ceiling. The calculator takes the nominal annual rate you type, divides it by 12 and holds that monthly figure flat through the interest-only and repayment phases, with no daily accrual. So it isn't the APR, and the output isn't a lender invoice. A variable-rate HELOC bill can move with the rate, even if you never draw again. Ask the lender how it sets the margin, which index it follows, whether rates are capped and when they adjust; the calculator won't make those up.
Can I enter a zero draw or zero interest-only years, and does it accept fractional years?
Zeros are fine, fractions aren't. Leave the draw at zero and the HELOC payments are modeled at zero too, with no rate or phase lengths needed; don't read those zeros as a made-up zero-percent quote. Zero interest-only years on a real draw means amortization starts immediately, so there's no interest-only payment and no step up to a higher one. Years must be whole: 2.0 reads as 2, never 20, and 5.0 reads as 5, never 50. Balloon plans aren't supported.
Does the tool reject a draw bigger than the capacity?
No. Nothing is trimmed quietly: the requested sum stays as typed, and payments are still shown for it, marked over the limit. Subtract the draw from capacity to get room left. If that comes out negative, you've asked for more than fits, and the negative figure isn't available credit. The excess is simply the draw beyond capacity. Say your existing debt already sits over the CLTV ceiling: capacity is zero, and the excess is the entire draw, without counting the old shortfall again. None of this means a line is approved.
If I multiply the monthly payment by the months, why do the totals differ, and do they include fees?
Fees count only if you financed them into the principal you entered; then they stay in the balance. Origination, transaction, annual and other separate fees are not added. Total payments are the interest of the interest-only period plus principal and interest during repayment, and principal is never double-counted. Current mortgage payments and net cash received aren't computed. Because totals come from exact monthly math rounded to the cent per category, multiplying a shown payment by its months can land slightly off. Trust the totals. Check real quotes with the lender, and keep in mind your home is at risk. The $100 billion cap on results is a limit of the calculator, not of lending.