HELOC Calculator: Credit Line and Monthly Payment
This HELOC calculator sizes your borrowing room from your lender's CLTV and secured debt, then estimates payments on your requested draw at a fixed rate.
What This Calculator Does
See how much more you could borrow against your home by entering its value, the CLTV your lender applies and the secured debt it counts. The calculator also models payments on the principal you request. First comes an interest-only phase with the balance held steady, then full monthly amortization at the same rate. The result isn't your equity, an approved line, cash in hand or a forecast of your coming variable-rate bills.
Who Is This For
If you're a Florida homeowner or agent testing a specific HELOC scenario, the numbers are only as solid as what your lender confirms about how it counts debt and which CLTV it uses. The same goes for fees, the rate and the terms of each phase. Don't swap in generic ratios or market defaults for those confirmed figures. Your current mortgage payments stay out of the HELOC figures shown.
How It Works
Begin with what the house is worth, every lien or secured loan your lender tallies, its top CLTV percentage and the sum you hope to take out. Taking out any money? Then the rate is required, along with interest-only years from 0–50 and repayment years from 1–50, whole numbers only. Leave the rate and both periods blank when the draw is 0. With 0 interest-only years, amortization kicks in immediately. Results cover your borrowing capacity, the room left (+) or overage (−), the monthly payment in each phase and the totals. Edit only figures you really have. Then run it again.
Frequently Asked Questions
Does the capacity figure show my home equity or an approved credit line?
No, it's neither. The tool multiplies your home's value by the CLTV you enter, rounds down to the cent, then subtracts the existing secured debt your lender counts; a negative result shows as zero extra capacity. Include every debt and credit line secured by the property on your lender's basis, not just your primary mortgage. If your lender counts a line at its full limit, enter the full limit. What you get is a scenario estimate, not your actual equity, an underwriting decision or a commitment. It doesn't assume a universal 85% rule.
Are payments based on my whole credit line or only what I draw?
Only the principal you ask for drives the payments. That balance counts as fully drawn from the outset and holds steady through each interest-only payment. Financed fees belong in the principal, so add them. Just remember that principal isn't the cash that lands in your account. Extra draws and revolving activity aren't simulated. Neither are paydowns during the draw period. Once repayment begins, the principal is paid off in full.
Does this estimate put a ceiling on my future payments?
No. Because the rate never moves in the model, the result can't cap what you'll pay later. The tool divides the nominal annual rate you enter by 12 and applies it unchanged during the interest-only years and the repayment years. That figure isn't the APR, and interest doesn't accrue daily. What you see is a scenario, not a statement from your lender. A real variable-rate HELOC bill can change with the rate even if you draw nothing new. Ask your lender for the margin, index, rate caps and adjustment terms, because the calculator doesn't invent them.
What happens if I enter a draw of zero, no interest-only years, or fractions of a year?
With a zero draw, the model shows zero HELOC payments and the rate and phase lengths are not required; those zero payments aren't a quote of a zero rate. With a draw above 0 and zero interest-only years, amortization begins at once, so the interest-only payment and the phase increase don't apply. Enter whole years: 2.0 reads as 2, not 20, while 5.0 counts as 5, not 50. Fractions get rejected. Balloon plans aren't supported.
What happens if I ask for more than my capacity?
The calculator keeps your full request instead of quietly trimming it. It still shows payments on the amount you asked for, flagged as over the limit. Room left is your capacity minus the draw; once that turns negative, your request exceeds the limit, and the negative figure isn't credit you can use. The excess is whatever you draw beyond capacity. Capacity bottoms out at zero: when existing debt already exceeds what the CLTV ceiling allows, capacity is simply zero, and the excess equals your entire draw, with no leftover shortfall added back. That doesn't mean a line is approved.
Are fees included in the totals, and why doesn't monthly payment times months match?
The total adds interest from the interest-only years to your repayment-phase principal and interest, without counting principal again on top. Origination, transaction, annual and other separate fees stay out, while anything you rolled into the principal you entered stays in the balance. The tool doesn't compute your current mortgage payments or the cash you'd net. Each total is built from exact month-by-month figures, and each category is rounded to the cent afterward, which means the displayed payment times the months can land slightly off the totals. Use the totals shown and check them against real lender quotes. Results stop at $100 billion, which is the calculator's ceiling and says nothing about how much a lender will lend.