HELOC Calculator
A HELOC is a revolving credit line secured by your home. See how large a line your equity supports, the interest-only payment during the draw period, and the fully amortizing payment once repayment begins.
How the heloc calculator works
A home equity line of credit, or HELOC, is a revolving credit line secured by your home — you borrow against the equity, repay, and borrow again as needs arise. The amount available depends on your home's value, what you still owe, and the lender's combined loan-to-value ceiling. A HELOC has two phases.
During the draw period you can pull funds and typically pay only the interest, keeping payments low. When the draw period closes, the repayment period begins and the balance amortizes into fully repaying payments. Rates are usually variable, so payments can move. This calculator shows the credit line, both payment phases, and how they differ.
Worked example: with home value of $450,000, balance owed (1st mortgage) of $260,000 and max combined ltv allowed of 85.00%, the heloc calculator shows home-equity credit line available of $122,500.
- Interest-only payment
- $425.00
- Repayment payment
- $520.69
- Remaining credit
- $62,500
- Interest if repaid in full
- $64,967
| Amount drawn | Home-equity credit line available |
|---|---|
| $25,000 | $122,500 |
| $50,000 | $122,500 |
| $75,000 | $122,500 |
| $100,000 | $122,500 |
The formula
Available credit equals the home value times the lender's combined LTV limit, minus the balance still owed on the first mortgage. The interest-only draw payment is the outstanding balance times the monthly rate. The repayment payment uses the standard amortization formula on the drawn balance over the repayment term.
- Available credit is bounded by the combined loan-to-value limit, which counts your first mortgage plus the new line together.
- The draw-period payment shown is interest-only, so it pays down none of the principal you have borrowed.
- Rates are variable and tied to an index; the estimate uses a fixed rate and does not project rate changes.
- The repayment payment assumes you carry the full drawn balance into repayment with no further draws or prepayments.
- Annual fees, closing costs, and any minimum-draw requirements are excluded from the payment figures.
Results are estimates for educational purposes and are not financial advice. Confirm exact figures with your lender or a licensed advisor.
Questions about the heloc calculator
What is payment shock at the end of a HELOC draw period?
It is the jump in your payment when the draw period ends. During the draw you may pay only interest, but once repayment begins you must cover principal and interest on a compressed schedule — often ten to fifteen years.
That can multiply your monthly payment severalfold overnight. Borrowers who treated the line as cheap money are sometimes caught off guard, so plan for the transition early.
How does the combined loan-to-value limit cap my credit line?
Lenders look at your first mortgage and the new HELOC together against your home's value. If a lender allows, say, 85 percent combined LTV, your first mortgage balance plus the maximum line cannot exceed 85 percent of the home's appraised value.
The more you still owe on the primary loan, the smaller the line you can open — even on a valuable home with substantial equity on paper.
Can my HELOC payment rise even if I don't borrow more?
Yes. Most HELOCs carry a variable rate tied to an index such as the prime rate. When that index rises, your rate and therefore your payment increase on the existing balance, with no new borrowing required.
This is a key difference from a fixed home equity loan. Some lenders offer fixed-rate lock options on portions of the balance to tame that volatility.
Is the HELOC Calculator free to use?
Yes. Every calculator on MortgageLoansCalculator is completely free, with no sign-up, login or paywall. Run as many scenarios as you like.
How does a HELOC work?
It is a revolving credit line secured by your home. During the draw period — often ten years — you borrow what you need and usually pay interest only; then a repayment period begins where you pay the balance down in full, at a usually variable rate.
How much can I borrow with a HELOC?
Usually enough to bring your combined loan-to-value up to about 80–85%. On a $400,000 home with a $250,000 first mortgage, an 85% cap leaves roughly $90,000 of borrowable equity.
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