This HELOC calculator answers the two questions a home equity line of credit comes down to: how large a line your home could support, and what the payment becomes when the interest-only draw period gives way to repayment. It is free, needs no signup, and every figure is worked out in your browser.
How to use the HELOC calculator
- Home value — a recent estimate. Lenders order their own appraisal, so treat yours as a starting point.
- Mortgage balance — everything still owed on the home, including any second mortgage or older equity line. Enter 0 if the home is paid off.
- Lender’s max CLTV — the combined loan-to-value cap the lender quotes, as a percentage.
- Amount drawn, interest rate, draw and repayment periods — take these from the lender’s HELOC disclosure, which the Truth in Lending Act requires before you open the plan.
Results update as you type, and the page address updates too, so a scenario can be bookmarked or compared side by side in two tabs.
The payment jump when the draw period ends
On a plan that lets you pay only the interest during the draw period — the case this calculator models — the balance does not shrink. When the draw period closes, the same balance has to be repaid, principal and interest, over a fixed number of years — and the monthly payment steps up at once. With the starting figures, a $10,000 balance at 10% costs $83.33 a month for ten years, then $132.15 a month for the next ten: 58.6% more, with no change in the rate at all.
Federal banking regulators illustrated the same effect for interest-only mortgages: a $200,000 loan at 7% cost $1,167 a month during a five-year interest-only period, then $1,414 once it started amortizing over the remaining 25 years, and $1,678 if rates had risen two points by then. That is why the calculator also shows the repayment payment at a rate two points higher. A HELOC’s rate is tied to an index such as the prime rate plus a margin, so the rate at the switch is unknown when you open the line.
The length of the repayment period matters as much as the rate. Repaying the same $10,000 over 20 years instead of 10 cuts the payment to $96.50, only $13.17 above the interest-only amount, but repayment-phase interest rises from $5,858.18 to $13,161.73. To see how each repayment payment splits between interest and principal, run the balance, rate and repayment years through the amortization schedule calculator.
How lenders size the line
The line starts from equity: a percentage of the home’s appraised value, minus what is already owed. The calculator shows your current loan-to-value alongside the result, and if existing balances already exceed the CLTV cap it says so rather than showing a negative line. Equity is only the ceiling, though. The lender also looks at income, other debts and credit history, so the approved line can be lower than the equity math allows.
Setting up a line costs money too: appraisal and application fees, points (one point is 1% of the credit limit), and closing costs, plus possible annual or per-draw fees. Those costs are not in this calculator’s payments.
Limits of this estimate
- One rate per phase. Enter the lifetime rate cap from your disclosure as the rate to see a worst case; variable-rate home equity plans must have one by law. The “2 points higher” line then goes past that cap, so it no longer applies.
- The full draw is assumed outstanding when the draw period ends. Drawing gradually means less interest during the draw period.
- Interest-only draw payments. Some plans require part of the principal in every draw-period payment, and on any plan you may choose to pay more (ask about prepayment fees). Either way the balance is smaller when repayment starts, and so is the jump.
- Rounding and the last payment. The level payment is rounded to the cent and the last payment settles the difference. That difference is usually small, but at very high rates over long terms the last payment can be far larger. The calculator shows the last payment whenever it is more than $1 away from the others.
If you are weighing a line of credit against replacing your first mortgage, the refinance break-even calculator shows how long closing costs take to pay back, and the mortgage payment calculator prices the first mortgage on its own. When a HELOC is meant to consolidate card balances, compare against the card’s own payoff path with the credit card payoff calculator — a HELOC turns unsecured debt into debt secured by your home.
Your numbers stay in your browser
Home values and balances are personal financial details. Every figure on this page is computed by JavaScript in your browser. Your inputs are kept in the page address — the part after the “?” — so you can bookmark a scenario or share a result; typing sends nothing to us, and our analytics receives page addresses without that part. A link you share carries your numbers with it, so send it only to people who should see them. Our privacy policy has the details.